forest management guidelines for major insects and diseases of

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Forest Management Guidelines for Major Insects and Diseases of Spruce, Pine and Aspen in eastern Canada

by

Peter de Groot , Anthony A. Hopkin, and Robert J. Sajan

Natural Resources Canada Canadian Forest Service

1219 Queen St. East Sault Ste. Marie, Ontario

P6A 2E5 CANADA

April 2003

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Summary This report provides forest management guidelines for minimizing the impact of insects and diseases in stands of spruce, pine and aspen in eastern Canada. There are hundreds of insects and diseases that attack trees; fortunately few of them are pests and even fewer are chronic, common and cause severe enough damage to warrant preventative or remedial action. These few are pests because they reduce growth and yield, form, and survival of the tree below an economic threshold. It makes sense that if we make significant financial investments in a forest, we should be willing to make an effort to protect these investments from serious losses. High value wood requires high quality trees that are free from stem defects and, or, produce wood fibre rapidly. Thus, insects and diseases that affect these qualities become of greater concern to the forest manager. Moreover, as the need for (or value of) wood intensifies, insects and diseases previously considered acceptable or inconsequential might become "pests" even though absolute populations have not changed. Any silvicultural treatment used to encourage tree growth and survival, or to

alter stand composition and structure, may influence the susceptibility of the stand to attack from insect and disease pests and the vulnerability to damage. Thus it is essential that forest managers consider the possible consequences of insect and disease pests while planning silvicultural treatments. The first section of this report a summary is provided that describes the major insect and diseases in Ontario and their damage. The second section lists the major insect and disease pests by tree species and provides a general overview of how silviculture can increase or decrease insect and disease problems. The third section describes the various insect and disease pests in more detail. For each pest, we provide a �thumbnail� sketch of the distribution, hosts, host damage and habitat in order to provide background to the main feature, which provides general prescriptions to reduce losses from the pest. The insects described in this report are the spruce budworm, jack pine budworm, white pine weevil, root collar weevils, pine engraver beetle, yellowheaded spruce sawfly, redheaded pine sawfly and forest tent caterpillar, and the diseases include, armillaria root rot, White pine blister rust, scleroderris canker, and tomentosus root rot.

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Acknowledgments We thank George Bruemmer, Al Stinson, and Vic Wearn for their support, advice and patience during the production of this report. The assistance of Betty Bennett with the collection, organization and synthesis of the information is much appreciated. Karen Jamieson edited the manuscript for which we are grateful. We thank the many current and former field technicians of the Canadian Forest Service who collected these data. We gratefully acknowledge the financial assistance of Tembec Inc., The Living Legacy Trust Fund of Ontario and the Canadian Forest Service of Natural Resources Canada.

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Table of Contents Page Summary �� 2 Acknowledgments ��. 3 1. Introduction �� . 6 2. Intensive Forest Management and Associated Pest Problems: An introduction . 7 3. Insects and Diseases of Plantations: Results from Forest Health Surveys in Ontario ��.. 10

3.1 Pests of Red Pine �� ...................... 12 3.2 Pests of Jack Pine. �� 18 3.3 Pests of Eastern White Pine �� ...................... 24 3.4 Pests of White Spruce �� 29 3.5 Pests of Black Spruce �� 33

4. General Considerations for Forest Management of the Major Insects and Diseases by Tree Species Working Group �� 46 4.1 Black Spruce �� 46 4.2 White Spruce �� 46 4.3 Jack Pine ��.. 47 4.4 Red Pine ��... 48 4.5 White Pine �� 48 4.6 Aspen �� 49

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Page

5. Forest Management Guidelines and Recommendations �� 50 Insects

5.1 Spruce budworm ................................................................................ 50 5.2 Jack pine budworm ............................................................................ 59 5.3 White pine weevil .............................................................................. 65 5.4 Root collar weevils ............................................................................ 74 5.5 Pine engraver beetle........................................................................... 77 5.6 Yellowheaded spruce sawfly ............................................................. 79 5.7 Redheaded pine sawfly ...................................................................... 83 5.8 Forest tent caterpillar ......................................................................... 86

Diseases

5.09 Armillaria........................................................................................... 88 5.10 White pine blister rust........................................................................ 91 5.11 Scleroderris canker............................................................................. 94

5.12 Tomentosus root rot ........................................................................... 97

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Introduction Any silvicultural treatment that you use to encourage tree growth and survival, or to alter stand composition and structure, may influence the susceptibility of the stand to attack from insect and disease pests and the vulnerability to damage. As a forest manager, it is essential that you consider the possible consequences while planning your silvicultural treatments. The consequences may be beneficial (reduced susceptibility and vulnerability) or detrimental (unacceptable economic loss). Our knowledge of the entomological and pathological consequences of various silvicultural treatments is incomplete and rudimentary. There are no long-term definitive studies that can predict and quantify with any reasonable accuracy the expected benefits or impact of a silvicultural treatment on pest populations. The changing and complex dynamics of a forest ecosystem, the long growing period, and changes in silvicultural practices are just a few of the formidable challenges. Can we afford to wait until the best answers come in, or do we proceed with imperfect knowledge, learn, and make adjustments along the way? If you expect simple, definitive and detailed prescriptions, you need not read any further − the answers are not here − or anywhere else. If you are prepared to follow general prescriptions based on current knowledge, experience, and reasoned common sense based on an understanding of insect and disease ecology (as imperfect as this all is), then we think you will find this report of value to you. This report provides a description of the common insect and disease pests that have occurred in the Boreal and Great Lakes - St. Lawrence Forest regions of Ontario, and

guidelines on how to mitigate losses through forest management and silviculture. In the first section, we provide a summary of the various insect and disease surveys of forest stands that have been completed in Ontario. This section is intended to introduce you to the �cast of characters� (insects and diseases) and their damage to the commercially important tree species in this area of Ontario. Recognizing that forest managers manage forests by tree species or working group, we have in the second section consolidated the main information from section three by tree species. The third section describes the various insect and disease pests in more detail. For each pest, we provide a �thumbnail� sketch of the distribution, hosts, host damage and habitat in order to provide background to the main feature, which provides general prescriptions to reduce losses from the pest.

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Intensive Forest Management and Associated Pest Problems: An Introduction Growing a forest from seed to maturity not only requires a long time but also a long-term view and commitment. Things to be considered range in scale from the autecology of the species and site characteristics to the larger picture including societal, economic and ecological values and products. It is seldom easy finding a balance that satisfies everyone. In response to historical land use conflicts, and to meet economic, ecological, and sociological needs, zoning the land base into intensive timber production, integrated zones, and protected areas has been proposed in many areas of the world and Canada. Although having areas where timber production has been designated as the primary purpose may help ease some of the conflicts and simplify some of the forest management practices, intensive forest management may bring on new problems of its own. One of these potential concerns is how insects and diseases will be affected by silvicultural practices. There are hundreds of insects and diseases that attack trees in Ontario; fortunately few of them are pests and even fewer are chronic, common and cause severe enough damage to warrant preventative or remedial action. These few are pests because they reduce growth and yield, tree form, and survival of the tree below an economic threshold. The accessibility of a forest stand, its productivity and ecological conditions, as well as prevailing ecological, social and

economic values determine in large measure the intensity of forest management and consequently the importance of insect and disease pests. The most logical sites for direct enhanced forest productivity are on accessible sites with potential for high productivity. It makes sense that if we make significant financial investments in a forest, we should be willing to make an effort to protect these investments from serious losses. High value wood requires high quality trees that are free from stem defects and, or, produce wood fiber rapidly. Thus, insects and diseases that affect these qualities become of greater concern to the forest manager. Moreover, as the need for (or value of) wood intensifies, insects and diseases previously considered acceptable or inconsequential might become "pests" even though absolute populations have not changed. Insects and diseases occur throughout all life stages of the forest. Some pests attack seedlings, others affect the sapling stage, usually before crown closure, while others attack mature or over-mature trees. Most plantations are established one-to-three years after harvesting. The black army cutworm (Actebia fennica) can appear within 1-2 years after a prescribed burn and devour vegetation including newly planted seedlings. Cut conifer stumps and logging slash left on-site after harvesting are attractive to adult root collar weevils (Hylobius spp.), which use this material for breeding. These insects girdle the root collar and main lateral root of young trees resulting in tree mortality, or they cause fluted root collars, which leave the trees susceptible to windthrow or secondary insects. The white pine weevil (Pissodes strobi) damages the central shoot (leader) of a tree and affects stem form and quality. Repeated infestations may reduce the tree to

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a subdominant one, which may become suppressed and die prematurely. This insect is typically found in young open-grown stands. The yellowheaded spruce sawfly (Pikonema alaskensis) and redheaded pine sawfly (Neodiprion lecontei) feed on the foliage of young open-grown trees causing severe defoliation and reducing tree growth or killing the tree. The spruce budworm (Choristoneura fumiferana), the jack pine budworm (Choristoneura pinus pinus) and the forest tent caterpillar (Malacosma disstria) are typically associated with mature trees and have historically been important in the dynamics of forest succession, renewal and nutrient cycling. These insects occur in widespread outbreaks (sometimes affecting millions of hectares), and are responsible for major wood losses. When these outbreaks happen, younger and more vigourous trees can also be vulnerable to damage. Unlike insects, diseases are generally more chronic and less extensive, and more focused on individual trees or groups of trees rather than entire stands. However, diseases, including decays and rots, are responsible for significant losses in merchantable timber normally exceeding that of the total harvest, in large part due to the mature nature of northern forests. Decays, which infect wounds, are responsible for the majority of lost fiber in natural forest. Root diseases such as armillaria (Armillaria spp.) and tomentosus root rot (Inonotus tomentosus), while causing mortality to newly planted trees, are also responsible for mortality and growth loss to older trees, and make trees susceptible to windthrow. Diseases such as the European race of scleroderris canker (Gremeniella abietina), and white pine blister rust (Cronartium ribicola) can cause

mortality of young trees, and are particularly successful in plantation environments. Prior to the widespread use of synthetic chemical insecticides, silvicultural methods of pest control were widely advocated and were often the only method that could offer some relief from pests. In recent years there has been resurgence in using silviculture to manage insects. Silvicultural techniques for pest management can normally be integrated with forest management and therefore they are appealing. Many are just good silviculture − plain and simple. A silvicultural approach for pest management is also attractive in the sense that it is much less controversial than pesticides and many approaches are environmentally benign. Silvicultural techniques in pest management manipulate the host or the environment so that they are less favourable or unacceptable to the insects or diseases deemed to be pests. Typically, populations or the amount of innoculum are reduced, sometimes substantially. The goal is to create a forest stand that is less susceptible and vulnerable to attack by pests and still economically sustainable. In this goal is a fundamental concept, that we attempt to reduce the pest problem, which is reasonable, but not to eliminate the problem, which is often untenable. Depending on the pest, some silvicultural approaches can offer a substantial benefit in reducing pest problems, while for others the pay back is less. Another important consideration is that silviculture is part of the pest management toolbox. Other methods of pest management, including the application or conservation of natural enemies such as parasites, predators or pathogens may, and at times, will, be needed to achieve a desired level of pest management.

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Many insects and diseases infest trees that are suffering in vigour, or ability to resist attack, because they were planted off-site, or because improper silvicultural methods were used. Silviculture aims to maintain and enhance the productivity of the forest. Sometimes, however, practices that are silviculturally sound and necessary (e.g., thinning) result in an increase in insect and disease problems. Here the forest manager must make a trade-off, but at least it will be an informed choice. Another trade-off that sometimes has to be made occurs when a silvicultural practice to reduce one pest promotes an increase in another pest. Again the best one can do is to make an informed choice. A very important caveat in the use of silviculture for pest management (and this can not be overemphasized enough) is that for many pests we are working with incomplete knowledge and working hypotheses rather than time-tested practices. Almost all of the silvicultural prescriptions described here have had limited development and testing in terms of geographic area, tree species, site characteristics, equipment and time, and cost. It is also important at the outset that we dispel the notion that silvicultural treatments can fully, and independently, solve pest problems. They can't. What they can do is to reduce the likelihood of trees being susceptible to attack or vulnerable to serious damage. They are used best when combined into an integrated forest pest management strategy that uses various approaches to manage insects and diseases at acceptable levels. This is not to say that silvicultural techniques can not be powerful tools for pest management. At times, avoiding a certain practices will mitigate pest damage (such as

not planting in areas where fresh stumps and logging debris will provide food for root collar weevils in high hazard areas). In other situations, using one silvicultural method over another (where this is possible) will lessen the impact of pests; for example, planting white spruce under an aspen canopy to reduce the impact of the yellowheaded pine sawfly. In the remainder of the report, that follows, we provide a "thumbnail" sketch of the distribution, hosts, host damage and habitat of each of the important insect and disease pests. Following this, we examine how various silvicultural treatments might be used (or shouldn't be used) to mitigate pest damage. A word of caution is in order. In our effort to condense, synthesize, and rationalize the existing knowledge into succinct and readable guidelines, we have had to generalize. Generalization always comes at the expense of ignoring some exceptions, smoothing over gaps in our knowledge, and worst, making things seem simple when they aren't. But in the spirit that a good plan now is better than a better plan too late, we present these guidelines. Furthermore, in the interest of keeping the reader with us, we have avoided an exhaustive and academic review of the literature. We surveyed the literature as abstracted to December 2001 and generally concentrated on and referenced the most recent and relevant work. We did not examine the effects of soil amendments (e.g., application of fertilizers) on insects and diseases, as there wasn't sufficient information to draw even the scantiest of prescriptions.

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Insects and Diseases of Plantations: Results from Forest Health Surveys in Ontario

INTRODUCTION Coniferous species make up the vast majority of Ontario�s industrial forests. Historically, the natural forest was the focus of attention both of industry and the research community. However, to meet increasing demands for timber and wood fibre, plantation management, or intensive silviculture, is seen as part of the solution, and significant efforts have been directed to the planting and tending of conifer tree species. Black spruce (Picea mariana [Mill] B.S.P.), and white spruce (Picea glauca [Moench] Voss), occupy over 2,300,000 ha, or about 50% of the productive forest in Ontario. Much of this resource exists as mixed wood forest. However, pure stands of spruce exist on more productive upland areas where plantations have been artificially created. Based on Ontario Ministry of Natural Resources (OMNR) figures, plantings of black spruce have increased since 1979, until recent years. Red pine (Pinus resinosa Ait.) is an eastern hard needle pine, uniform in growth and form with little genetic variation. Through the 1980s, the OMNR produced and planted 5 to 7 million red pine seedlings annually (OMNR 1989). Jack pine pine (Pinus banksiana Lamb.) is a hard needle pine characteristic of the northern, boreal forest. Throughout the 1980s about 51.5 million jack pine seedlings were produced annually at the Ontario Provincial Tree Nurseries and planted across northern Ontario (OMNR1989). It usually grows in even-aged pure or mixed stands on dry soils

(Burns and Honkala 1990). Eastern white pine (Pinus strobus L.) is a soft needle pine that has been widely planted in Ontario and is considered to be the most valuable softwood lumber in eastern Canada. During the mid to late 1980s, the OMNR annually produced and planted some 10 million white pine seedlings (OMNR1989). White pine grows on nearly all the various soils within its range, but generally grows and develops best on well-drained sandy soils of low to medium site quality. Throughout northern forest ecosystems, there are hundreds of species of insects and diseases that attack trees at various stages of growth. Fortunately for the forest manager, few of these reach pest status. These few are pests because they affect form, and reduce growth and yield, and survival of the tree below an economic threshold. These thresholds are lower in high-value, intensively managed sites than in extensively managed sites where little investment has been made. In addition to the greater economic investment in planted and tended sites, mono-cultural plantations are sometimes more vulnerable to pests. that are not normally a problem in natural forests. Most published literature on forest pests in Canada comes from work in naturally regenerated forests. The actual incidence and level of damage caused by insects and diseases to plantations are less certain. Little information is available on the relative susceptibility of pure stands at various stages. Because of this lack of information on pest problems in our

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managed forests, the then Forest Insect and Disease Survey (FIDS) made an extensive survey of pine and spruce plantations in Ontario between 1980 and 1989, to determine the level of damage caused by forest pests. The purpose of this document is to reassess the results of these surveys to determine both, what levels of pest attack might be expected in spruce and pine plantations, and the potential susceptibility to pests at various stages in the plantation�s history Methodology Surveys of pine and spruce plantations were taken throughout the province between 1980-1989. Surveys for each tree species occurred at three-year intervals. Stands were randomly selected in each of three height classes: < 2.0 m; 2.0 - 6.0 m; and > 6.0 m. The total number of plantations and trees evaluated in each height class were as per Table 1. Within each height class, selections were limited to one plantation per 1,000 km2, with each stand being of a minimum of 5 ha in size. Plantations were sampled twice in each growing season, once in mid June to mid July, followed by a visit in late July to early August. On the first visit, one hundred and fifty trees were marked and evaluated on ten transects, each containing fifteen trees; these same trees were re-evaluated on the second visit. Different plantations were selected for evaluation during each sampling year. Within a transect each tree was assessed for the presence of pests and corresponding levels of damage and defoliation. Damage levels were assessed on the basis of incidence for non-foliar pests (armillaria, diplodia, weevil, stem and

gall rusts); trace-light (T-L) damage = 1-5% trees affected, moderate-severe (M-S) damage >5% trees affected. For frost and defoliating pests (spruce budworm, spruce coneworm, spruce sawfly, spruce needle rust,) damage was based on average defoliation levels; trace-light damage = 1-25%, moderate-severe damage > 25%. For all pine sawflies the number of colonies was assessed per tree due to the late season nature of defoliation for this group of insects. Table 1. Conifer plantations and species, evaluated for pest damage. Species Avg ht. No. stands No. trees Red Pine <2 m 31 4,650 2-6 m 32 4,800 > 6 m 28 4,200 Jack Pine <2 m 54 8,100 2-6 m 60 9,000 > 6 m 48 7,200 White Pine <2 m 56 8,400 2-6 m 53 7,950 > 6 m 52 7,800 White Spruce<2 m 76 11,400 2-6 m 83 12,450 > 6 m 66 9,900 Black Spruce<2 m 66 9,900 2-6 m 54 8,100 > 6 m 29 4,350 Results for each pest are displayed on the basis of the percentage of plantations in each height class that were affected (Figs 1-5) along with the approximate damage levels in affected plantations. Within affected plantations the average

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incidence of each pests, including defoliation where applicable, was calculated and displayed in Tables 2-6. RESULTS Pests of Red pine Pine False Webworm Acantholyda erythrocephala L. The pine false webworm, an introduced pest first detected in Ontario in 1961, was most common on trees <6 metres (Figure 1). In the <2 m height class about 8% of the trees from affected plantations sustained an average of 3% defoliation (Table 2). Higher damage levels (8.5%) were evident in the 2-6 m plantations. In the over 6 m height class, only 4% of the plantations were infested and trace defoliation (1%) was recorded

(Table 2). The survey would suggest that red pine in the 2-6 m height class is most susceptible to pine false webworm attack. The pine false webworm has historically been a problem in red pine plantings < 4 m in height. Infestations routinely lasted two to three years, caused considerable amounts of defoliation and growth loss, but resulted in limited mortality. However, in 1995, infestations in semi-mature trees, 12 to 18 m in height were recorded for the first time in Ontario in south central Ontario (Howse 2000). Following two years of severe defoliation whole tree mortality was reported in these plantations. In Ontario, red pine has been widely planted in even-aged stands for over 70 years, primarily in south central and southern Ontario. In general, monocultural pine plantations are more vulnerable to certain pests at various stages of their development and during peak periods of major outbreaks, such as the one by pine false webworm in the 1990s. In these instances a single application of a contact or stomach chemical insecticide as the larvae emerge in the spring effectively controls populations (Helson and Lyons 2000). Redheaded Pine Sawfly Neodiprion lecontei Fitch The insect was present in about 25-30% of plantations in the < 2 m and 2-6m height classes but not in plantations of >6m (Figure 1). In affected plantations about 2% (maximum 4%) of trees were attacked by this insect (Table 2). The number of colonies per infested tree was recorded rather than defoliation, which occurred after field assessments. On infested trees an average of 2 colonies

Pine false webworm damage

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per tree was recorded during the survey period on plantations < 6m. Wilson et al. (1992) established a relationship between colony number and defoliation based on tree height. Roughly, two colonies (50 larvae each) could completely defoliate a 0.6m red pine, whereas a 2m tree would require 15 colonies for complete defoliation. The results of the survey would suggest that the redheaded pine sawfly could damage young trees. The redheaded pine sawfly is considered a serious pest of red pine plantations in southern and central Ontario (Rose et al.1999). It typically feeds on young, open-grown trees, less than 5 m in height, frequently resulting in extensive whole tree mortality in young plantations (Martineau 1984). Pockets of high populations often develop along the edges of plantations bordered by hardwoods or on open-grown trees on knolls (Drooz 1985). Although not evident during the survey period, defoliation levels of 100% are frequently reported in immature red pine plantations in southern Ontario and a single year of severe defoliation can result in reduced growth rate and branch and whole tree mortality. Trees growing under stress are more susceptible to attack by this sawfly. Avoid planting red pine off-site; on shallow, low nutrient, extremely dry sites or in low-lying frost pockets. Severe competition from hardwood regeneration and bracken fern should be avoided (Drooz 1985). Maintaining trees in a healthy, vigourously growing condition by exercising sound silvicultural practices will greatly reduce the impact of this insect. In high value plantations or seed orchards a biological insecticide such as Lecontvirus, may be applied when the

larvae are first observed in mid to late July (Cunningham et al. 1985). Red Pine Sawfly Neodiprion nanulus nanulus Schedl The red pine sawfly was detected in all height classes with 11-22% of plantations affected in <2m and 2-6m plantations respectively (Figure 1). The highest populations (number of colonies) were observed on the smaller trees (<2m) with colony numbers decreasing with tree height (Table 2). However, this number of colonies per tree could result in moderate to severe defoliation, (>25%) in the <2 m trees and light to moderate levels (>5%) in the >2 m tall trees. However, only a limited number of trees were infested in all plantations. The red pine sawfly, only consumes old needles and therefore whole tree mortality usually does not occur following a single year of severe defoliation. But where defoliation continues for several, years a high percentage of trees may be killed. Over-mature red pine are very susceptible to attack by this sawfly. European Pine Shoot Moth Rhyacionia buoliona (D. & S.) The European pine shoot moth, which is found primarily in southern Ontario, was detected only in plantations <6 m in height (Figure 1). The impact of this insect was measured by the percentage of trees with leaders or laterals affected. This survey found that the incidence of leaders and laterals attacked on trees <2 m averaged 28% (maximum 79%) in affected plantations. This number was extremely high when compared to the larger height classes (>2m), where the average incidence of damaged leaders

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and laterals was less than 2% for trees 2-6m (Table 2). No damage was detected on either leaders or laterals in the >6 m height class throughout the entire survey. Young, open-grown pines < 10 m in height are more susceptible to attack and repeated damage to red pine can result in main stem deformity (Rose et al.1999).

The European pine shoot moth, an introduced species, kills terminal and lateral buds resulting in dead, spiked tops (Drooz 1985). The killing of the terminal buds and the development of several lateral buds into potential leaders often results in forked stems reducing the merchantability of pines. As with sawflys, young open-grown red pine less than 8 m in height are very susceptible to attack and canopy closure should be promoted as soon as possible where this pest is a concern. The most important natural control factor is low winter temperatures. The pruning and removal of infested shoots in mid May has proven to be a successful control method (Martineau 1984). When populations are extremely high, an application of a contact or stomach insecticide, with good residual properties, should be applied in early June.

Armillaria Root Rot Armillaria spp. Armillaria root rot was found in 8% of the plantations surveyed (Figure 1). During this survey only trees killed by armillaria were counted, thereby underestimating the total infected. A more accurate assessment would require destructive sampling of living trees. Damage was most frequently detected in the <2 m height class and caused an average of 3% mortality in 19% of the plantations (Table 2). In the >6 m height class an average mortality rate of 2% was detected in 4% of the plantations. No damage was found in the 2-6 m plantations. The survey suggests that the incidence of Armillaria root rot or at least mortality, decreases as the plantations age.Whitney (1988) reported annual mortality rates of about 0.5% in young red pine plantations, although up to 16% of the trees were killed by this disease in one plantation.

Armillaria Root Rot Armillaria root rot causes mortality when the overall vigour of the host declines as a result unfavorable environmental conditions, particularly drought (Canadian Forest Service 1994). The disease kills trees singly or in small, circular pockets, especially in

European pine shoot moth damage

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monocultural plantation. Heavily infected trees experience radial growth loss and butt rot, and are prone to wind throw damage. Armillaria root rot is very difficult to control and avoidance is the best strategy. Careful site selection and good management practices that maintain a healthy, vigourously growing stand are strongly recommended. Management of this disease is feasible only during harvest and stand establishment. Pre-harvest surveys are valuable when armillaria is considered a problem. In stands known to have a history of the disease colonization of stumps can result in significant losses to future stands. In high-value conifer plantations, stump removal or pushover logging has been practiced to reduce inoculum after harvesting (Morrison and Mallett 1996). Using locally adapted seed sources for indigenous species is recommended to increase the fitness of the plantation. Where armillaria is known to be a problem, use of more resistant pine species is recommended whenever practical. Pine Needle Rust Coleosporium asterum (Dietel) Syd. & P. Syd. Pine needle rust was found affecting all height classes in the survey. In the < 2 m class, about 25% of the plantations were affected (Figure 1). In these plantations about 40% of the trees (maximum 100%) were defoliated at low (5%) levels (Table 2). Similar damage levels were detected in the 2-6 m height class, where about 35% of the plantations were affected (Figure 1). In the affected plantations an average of 37% of trees were infected by needle rust, though generally at low levels (< 4% defoliation). In the >6 m height class only 7% of the plantations were affected.

Average incidence of the disease was about the same in affected plantations (31%) but defoliations levels were higher (21%). Pine needle rust infects the current year�s foliage late in the fall; it usually dies and falls from the tree following summer. Defoliation caused by this needle rust has been reported, almost yearly, in red pine plantations in southern Ontario. In some cases the infected needles will persist on the tree for three years. Infections that result in whole tree mortality are rare because current year�s needles are not affected until late in the fall, after the growing season is completed (Hiratsuka. and Powell 1976). The disease is rarely a concern, except as an additional stress factor, or in years where populations are unusually high. The removal of any alternate host plants, Aster spp., and (goldenrod) Solidago spp., within 300 m of pine plantings should also provide some level of control when required (Davis and Meyer 1997). Mortality due to this rust is not a concern, but repeated years of moderate to severe defoliation can result in reduced vigour in younger trees (Ziller 1974). Scleroderris Canker Gremmeniella abietina (Lagerb.) M. Morelet Scleroderris canker was observed in about 20% of the <6 m plantations, and less than 5% of those >6 m (Figure 1). In affected plantations <6m the disease was present on about 33% of trees (Table 2), and 7% of trees >6m were infected. Two races of this fungus, the North American and the European, have been identified in Ontario (Hopkin and McKenney 1995). The European race is

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generally more virulent and capable of killing mature red pine, but it is very difficult to distinguish between the two races (Laflamme 1991).

European race of sclerroderris on red pine Although the North American race affects jack pine as well, scleroderris canker is primarily a problem of red pine in central Ontario where the introduced (European race) exists (Hopkin and McKenney 1995).Young red pine (< 0.5 m) infected with the European race usually die in one year. The disease does not occur below 44o30� in Ontario (Hopkin and McKenney 1995); on this basis, hazard zones based on climate have been proposed for Ontario (Venier et al. 1998). When grown in a high hazard zone, scleroderris can be controlled through pruning and sanitation (Hopkin and Laflamme 1995). The disease is generally a result of nursery infection and can be greatly reduced by the on-going inspection of stock prior to shipment, or removal of susceptible pine species windbreaks around nurseries. Fungicides can be used effectively in nurseries north of 44o30�, south of this area they are not necessary. Spraying should begin in the early spring once air temperatures rise above 0oC (Hopkin and Laflamme 1995).

Pine Needle Cast Lophodermium pinastri (Schard.:Fr.) Chevall. Pine needle cast was found to be affecting all of the height classes surveyed (Figure 1). In the <2 m class, 6.5% of the plantations had an average incidence of 5%, and an average of 1% defoliation (Table 2). In the 2-6 m plantations the incidence of infection doubled to 10% (maximum 28%), at 19% of the locations. However, the defoliation levels remained very low. The highest damage levels occurred in the >6 m height class, with 7% of the plantations infected. Within these plantations, 31% of the trees were infected (maximum 60%), and average defoliation levels of 22% (Table 2). Needle casts are not normally a problem in natural forests. However, consecutive years of heavy infection rates by pine needle cast can result in a reduction in growth and overall vigour, leading to stunted seedlings and saplings (Nichols and Skilling 1974). A single year of severe defoliation can kill nursery seedlings (USDA Forest Service 1979). In older age classes several years of severe infection will result in reduced growth and vigour, but generally whole tree mortality does not occur (Myren 1994). Fungicide applications have been effective in controlling needle cast in nurseries (Minter 1981).

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1 2 3 4 5 6 7 8 9 100

1 0

2 0

3 0

4 0

Perc

ent

stan

ds a

ffect

ed

To ta l T - L M - S

1 = R e d h e a d e d p in e sa w fly, 2 = P in e fa lse w e b w o rm , 3 = E u ro p e a n p in e sh o o t m o th 4 = E u ro p e a n p in e sa w fly 5 = R o o t co lla r w e e v il, 6 = S c le ro d e rris ca n ke r, 7 = P in e n e e d le ru s t, 8 = P in e n e e d le ca s t, 9 = A rm illa ria ro o t ro t, 1 0 = B la ck s ta in ro o t d ise a se

H e igh t c lass < 2m

1 = R e d h e a d e d p in e s a w fly , 2 = P in e fa ls e w e b w o rm , 3 = E u ro p e a n p in e s h o o t m o th 4 = E u ro p e a n p in e s a w fly , 5 = R o o t c o lla r w e e v il, 6 = S c le ro d e rr is c a n k e r, 7 = P in e n e e d le ru s t, 8 = P in e n n e d le c a s t, 9 = A rm illa r ia ro o t ro t, 1 0 = B la c k s ta in ro o t d is e a s e

H e ig h t c la s s 2 - 6 m

1 2 3 4 5 6 7 8 9 1 00

1 0

2 0

3 0

4 0

Perc

ent

stan

ds a

ffect

ed

To ta l T - L M - S

1 = R edheaded p ine sawfly, 2 = P ine fa lse w ebworm , 3 = E uropean p ine shoo t m oth 4 = E uropean p ine saw fly, 5 = R oot co lla r weevil, 6 = S cle roderris canker, 7 = P ine need le rust, 8 = P ine need le cast, 9 = A rm illa ria roo t ro t

1 2 3 4 5 6 7 8 90

10

20

30

40

Perc

ent

stan

ds a

ffect

ed

To ta l T - L M - S H eigh t c lass > 6 m

Figure 1. Percent of red pine plantations affected by various pests in three height classes, < 2m, 2-6m, and > 6m.

18

PESTS of JACK PINE Jack Pine budworm Choristoneura pinus pinus Free. Jack pine budworm defoliation was encountered in about 20-25% of all plantations < 6 m (Figure 2). In the affected plantations 22% of the trees were infested, but with only <2% defoliation. In the >6 m class, 13% of the plantations were infested, averaging 6% defoliation on 58% of the trees. The survey indicates that the level of damage increases with the height of the plantation. The defoliation/height relationship is well known, as jack pine budworm normally attacks semi-mature to mature stands. The relatively high incidence of budworm on smaller trees was surprising, although it should be noted that jack pine plantations assessed were generally adjacent to mature stands. The plantation survey data does not reflect the full impact of this infestation, although it is generally assumed that younger stands are not at significant risk to the budworm.

Jack Pine budworm damage

Defoliation by the jack pine budworm will last two to three years and results in

significantly reduced growth, and top kill or multiple leaders (Hopkin and Howse 1995). Mortality, while serious in some situations is usually much lower than that caused by the spruce budworm, When an infestation of jack pine budworm does occur, biological insecticides may be applied to protect severely infested stands. Long-term silvicultural practices include the removal of mature trees, which produce heavy flower crops that encourage increases in jack pine budworm population levels (Hodson and Zehngraff 1946).

White Pine Weevil Pissodes strobi (Peck) Leader damage caused by the white pine weevil was detected in a high percentage of stands <6 m in height (Figure 2). In the <2 m height class 59% of the stands were infested, averaging 4% (maximum15%) of the leaders damaged. In the 2-6 m class 50% of the plantations were found to be infested, averaging 3% (maximum 13%) leader damage, and in the >6 m height class, 12% of the stands had an average of 1% (1-2%) of the leaders damaged. The white pine weevil is the most prevalent pest of pine species in Ontario. The damage it causes to white pine will reduce the total volume of the tree and degrade the remaining volume. Repeated attacks will seriously affect tree form. While it is not as damaging to jack pine as it is to white pine, this insect is one of the more prevalent plantation pests. The overall incidence of white pine weevil, jack pine tip beetle, and eastern pine shoot borer decrease as the plantations age and increase in height growth. The surveys indicated that the 2-6 m trees are

19

most vulnerable to attack. During years of high populations, control measures should be considered, especially prior to canopy closure. Insecticides can be applied when adults are active, but the physical removal of infested shoots and leaders is also a very effective control and should also be considered. In addition to mechanical and chemical control measures there is evidence that site (Lavallee 1992a) and stand (Wallace and Sullivan 1985) conditions might influence the level of damage caused by this pest. Eastern Pine Shoot Borer Eucosma gloriola Heinr. Leader damage caused by the eastern pine shoot borer was detected in > 50% of plantations <6m, whereas only about 12% of plantations >6 m were found to be affected (Figure 2). In all height classes, 2-3% of the trees in affected plantation had leader damage (Table 3). Damage to laterals (not shown) was also evident in all height classes, ranging from an average of 2%, 7, and 5.5% respectively in the three height classes. The survey would suggest that the overall incidence of this insect is low. However, infested main stem terminals can result in significant loss of height growth and the deformity of the main stem, especially in younger plantations. When the damage occurs on the lateral branches, excessive branching in the upper half of the crown can occur (USDA Forest Service 1979). This pest is most common on open grown trees (Rose et al. 1999) and some work has shown that the insect prefers jack pine of an intermediate height (Wong et al. 1966). Jeffers (1978) noted a relationship between jack pine seed source and damage; stock originating

from the coldest sources was more vulnerable to damage. Other surveys (McKeague and Simmons 1978) have found this insect at damaging levels and have recommended pruning as a standard control measure.

Eastern pine shoot borer damage

Jack Pine Tip Beetle Conophthorus resinosae Hopk. ( = banksianae McP.) The jack pine tip beetle was found to be infesting all height classes in the plantations surveyed (Figure 2). This pest attacks both leaders and laterals, but for the purpose of this survey, only leader damage was assessed. In the < 2 m height class, 26% of the plantations (Figure 2) were infested, with an average of 1.5% of trees showing leader damage (Table 3). In the 2-6 m class, 22% of the plantations were found to have an average of 3% (maximum 10%) leader damage (Table 3), and in the >6m class 1% of the trees showed leader damage in 17% of the plantations. The data would suggest that there is an overall decrease in the incidence of leaders attacked with the increase in plantation height. The beetle does not generally cause mortality or loss of vigour, but can damage the terminal leader resulting in a

20

loss of height growth and the deformity of the main stem. When the damage occurs on the lateral branches, excessive branching in the upper half of the crown may occur (USDA Forest Service 1979). De Groot (1991) however, reported that populations are seldom high or sustained enough to cause significant damage. Jack Pine Sawfly Neodiprion pratti banksianae Roh. The jack pine sawfly was found to be infesting approximately 10% of the 162 plantations surveyed in all height classes (Figure 2). Incidence, which was determined by presence of colonies of this insect was low in all height classes (Table 3), the highest value recorded during the survey was 5.0% in 2-6m trees (Table 3). Older, open grown trees are more subject to defoliation than young trees and even-aged stands and plantations are especially attractive (USDA Forest Service 1985). Several consecutive years of defoliation will result in whole tree mortality. Jack pine sawfly outbreaks have occurred periodically in mature and semi-mature jack pine stands in Ontario. Severe defoliation for two years or more will result in growth loss and a reduction in overall vigour (Martineau 1984). An application of a stomach or contact insecticide is recommended to control outbreaks. Armillaria Root Rot Armillaria spp. Armillaria root rot was detected in all height classes of the jack pine plantations that were surveyed, but was most common in stands <6m (Figure 2). In the <2 m height class, 44% of the stands were affected, with an average of

1% mortality (1-3%) in affected plantations. In the 2-6 m class, 28% of the plantations also showed mortality of 1%, (1-3%). Only 4% of plantations >6m were found with armillaria symptoms, and in these about a 1% of trees were infected. Whitney (1988) reported that jack was less susceptible to armillaria than spruce species and that annual mortality caused by the disease was close to 0.5%. Trees are most at risk to armillaria when the host vigour declines as a result of unfavourable environmental conditions, particularly drought. Trees may die individually, or in small, circular pockets, especially in mono-cultural plantations. Heavily infected trees experience radial growth loss, butt rot, and are prone to wind throw because of weakened root systems (USDA Forest Service 1979). Armillaria root rot is very difficult to control, once established. Careful site selection and good management practices that maintain a healthy, vigourously growing stand are strongly recommended. Management of this disease is feasible only during harvest and stand establishment (Davis and Myer 1997). Although costly, the removal of old, infected stumps, and root raking should be considered, especially if the area to be replanted is to be used as a seed orchard or for another high value purpose (Whitney 1988). Stump removal followed by a short fallow period has helped to reduce secondary inoculum. Scleroderris Canker Gremmeniella abietina (Largerb.) Morelet Scleroderris canker was found in all height classes of the jack pine plantations surveyed (Figure 2). In the <2m height class only 5% of the

21

plantations were affected with an average of 21% (maximum 59%) of the trees infected (Table 3). In the 2-6 m height class 10% of the plantations contained scleroderris, with an average of 18% of the trees infected (Table 3). About 2% of plantations > 6 m in height, contained the disease but only 1% of the trees in these plantations were infected. Two races of this fungus, the North American and the European, have been identified in Ontario. The European race is generally more virulent and capable of killing mature red pine but is restricted to south-central Ontario (Hopkin and McKenney 1995). However, jack pine is resistant to the more virulent European race. The North American race of Scleroderris canker be a problem in seedlings, but young, vigourously growing jack pine trees, over 2m in height, normally outgrow the infection and survive (Dorworth and Davis 1982). Cankered trees that survive the attack will sustain a volume and quality loss in the main butt log due to the defect (Davis and Meyer 1997). Infection rates are most severe in low areas, such as frost pockets. The clipping and removal of infected branches is an effective control, especially during the first year or two of infection. Removing the lower one third of the branches from trees in an infected plantation, has produced successful levels of control in heavily infected areas. Pine Needle Rust Coleosporium asterum (Dietel) H. Sydow & Sydow Pine needle rust was found primarily in plantations < 6m in height (Figure 2). In the <2 m height class, 44% of the plantations were affected, averaging 4% defoliation on 27% of the trees (Table

3). In the 2-6 m height class, 38% of the plantations were affected, averaging 4% defoliation on 39% of the trees. In the >6 m height class, only 4% of the plantations were affected, with an average 1% defoliation on 42% of the trees (Table 3). Various levels of defoliation of jack pine caused by this needle rust are reported almost yearly in jack pine areas. While this disease is normally of little concern, repeated years of moderate to severe defoliation can result in reduced vigour, however serious impact is insignificant on mature and semi-mature trees (Ziller 1974). Needle Cast Davisomycella ampla (J. Davis) Darker Lophodermium seditiosum Minter, Staley & Millar Pine needle cast was found affecting all height classes (figure 2). In the <2 m height class, 20% of the plantations were affected, causing an average of 17% defoliation on 20%, of the trees (Table 3). In the 2-6 m height class, 42% of the plantations had an average of 4% defoliation on 13% of the trees. In the >6 m class, 19% of the plantations were affected, averaging 15% defoliation on 35% of the trees. A single year of severe defoliation can kill seedlings and several consecutive years of severe infection will reduce growth and vigour in older age classes, but generally mortality does not occur (Myren 1994). Western Gall Rust Endocronartium harknessii (J.P. Moore) Y. Hirats. Western gall rust was found to be affecting all height classes of jack pine. In the <2 m height class, 46% of the plantations were found to contain the disease with an average of 7% of the

22

trees affected (Table 3). In the 2-6 m height class, 50% of the plantations contained gall rust, with an average of 12% (maximum 80%) of the trees infected. In the >6 m height class, 48% of the plantings were affected, and the average incidence of 21% (maximum 85%).

Western gall rust damage

This rust is considered as a major disease of hard pines (Hiratsuka 1987). Galls caused by this rust fungus can encircle either the main stem of young trees or branches; portions of the host distal to the galls subsequently die. Young trees (normally <1 m) with main stem infections normally die and those that survive are prone to wind breakage. Severe infections of young trees can distort the growth form (Myren, 1994). Mortality is common in young jack pine stands although Gross (1983) did not consider this to be significant. Juzwik and Chong (1990) found cumulative mortality in jack pine plantations < 10 years of age to average 3.4%. Stem Rusts Cronartium comptoniae Arthur

Cronartium comandrae Peck Cronartium coleosporioides Arthur f. sp colesporioides For survey purposes these three stem rusts were treated similarly, as each causes cankers that can girdle and kill branches and stems of trees in all age classes (Myren 1994). Stem rust damage was detected in 17% of the plantations surveyed, with all height classes affected (Figure 2). In the <2 m height class 15% of the plantations were found to have about 2% of the trees infected. In the 2-6 m height class, 20% of the plantations surveyed also showed an average infection of 2% (maximum 10%). In the >6 m class, only 5% of the plantations had stem rust, however, on average 6% (maximum 15%) of the trees were infected, however this latter group is more likely to survive infection by the rust. Stem rust fungi commonly infect and kill pine seedlings, and the formation of cankers on the main stems of semi-mature trees can girdle and kill the trees. Cankers usually develop, extend to a height of one meter or more and serve as entry points for other decay fungi (Myren 1994; Ziller 1974).

23

1 2 3 4 5 6 7 8 9 10 110

10

20

30

40

50

60

70

Perc

ent s

tand

s af

fect

ed

To ta l T - L M - S H eight c lass < 2m

1 = Jack p ine budworm , 2 = Jack p ine saw fly, 3 = W hite p ine weevil, 4 = E uropean p ine shoot borer,5 = Jack p ine tip beetle , 6 = P ine need le rust, 7 = P ine need le cast, 8 = W estern ga ll rust, 9 = S tem rust, 10 = S c leroderris canker, 11 = A rm illa ria root ro t

1 2 3 4 5 6 7 8 9 10 110

10

20

30

40

50

60

70

Perc

ent s

tand

s af

fect

ed

To ta l T - L M - S H eight c lass 2 - 6 m

1 = Jack p ine budworm , 2 = Jack p ine saw fly, 3 = W hite p ine weevil, 4 = E uropean pine shoot borer,5 = Jack p ine tip beetle , 6 = P ine need le rust, 7 = P ine needle cast, 8 = W estern ga ll rust, 9 = S tem rust, 10 = S c leroderris canker, 11 = A rm illa ria root ro t

1 2 3 4 5 6 7 8 9 10 110

10

20

30

40

50

60

70

Perc

ent s

tand

s af

fect

ed

To ta l T - L M - S H eight c lass >6m

1 = Jack p ine budworm , 2 = Jack p ine saw fly, 3 = W hite p ine weevil, 4 = E uropean p ine shoot borer,5 = Jack p ine tip beetle , 6 = P ine need le rust, 7 = P ine need le cast, 8 = W estern ga ll rust, 9 = S tem rust, 10 = S c leroderris canker, 11 = A rm illa ria root ro t

Figure 2. Percent of jack pine plantations affected by various pests in three height classes, < 2m, 2-6 m, and > 6m

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PESTS OF EASTERN WHITE PINE White Pine Weevil Pissodes strobi (Peck) This insect was found in plantations of all height classes during the survey (Figure 3). In the <2 m height class, 57% of the plantations were affected; an average of 8%, (maximum 29%) of the trees had weevil damage (Table 4). In the 2-6 m height class, 68% of plantations had weevil damage, with an average of 12% (maximum 60%) of the trees infested. Weevil damage was also found in 40% of plantations > 6 m tall. In these taller plantations, an average of 6% (maximum 33%) of the trees were damaged. The surveys results suggest that plantations between 2-6m tall are most likely to have weevil damage.

White pine weevil damage

White pine weevil is the most important insect pest of white pine in eastern Canada. Two or more years of terminal growth are killed as a result of weevil attack, which seldom causes mortality but usually results in a distorted main stem. Eastern white pine is routinely attacked and damaged by this weevil until the trees are over 10 metres tall or r

crown closure has occurred (Rose et al.1999). While insecticides have been tested for weevil control, a silvicultural approach that modifies the density of the stand to produce an unfavourable environment (Wallace and Sullivan 1985) along with removal of infected leaders is generally the preferred and most effective form of weevil control. Eastern Pine Shoot Borer Eucosma gloriola Heinrich The eastern pine shoot borer occurs throughout the natural range of white pine in Ontario. Damage caused by this shoot borer was recorded in all height classes, but primarily in plantations < 2m in height (Figure 3). In the < 2 m height class, 27% of the plantations were infested, with an average of 3% of the trees affected (Table 4). In the 2-6 m height class, 13% of plantations were infested, with an average of 2.6% of trees affected. Only 8% of plantations > 6 m tall contained this insect, but the percentage of trees infested in these plantations increased to 8% (max 22%). Infested main stem terminals result in significant loss of height growth and the deformity of the main stem, especially in the 2-6 m height class. When the damage occurs on the lateral branches, excessive branching in the upper half of the crown may occur (USDA Forest Service 1979). Pine Bark Adelgid Pineus strobi (Hartig) In the < 2 m height class, 36% of the plantations were affected by the adelgid. In affected plantations an average of 10% of the trees were infested with a average of one colony per tree. In the 2-6 m height class, 38% of the plantations were affected, again averaging 10%

25

(maximum 32%) of the trees infested with a density of a single colony per tree. In the > 6 m height class, 50% of the plantations were affected and the percentage of infested trees increased to 32% (max100%), but the number of colonies remained constant at one per tree. The survey indicates that as the trees grow, the incidence of infested trees can increase. Serious injury by the pine bark adelgid has been reported in Ontario (Rose et al.1999), although normally, healthy, mature trees suffer no serious damage (USDA Forest Service 1985). Pine Spittlebug Aphrophora parallela (Say) During the surveys, this pest was found in all height classes. In the < 2 m height class, 54% of the plantations were infested, averaging 10% (maximum 76%) of the trees affected. In the 2-6 m height class, 43% of the plantations were infested, but the average number of trees in the plantations that were infested was 16% (max 100%). In the > 6 m class, 31% of the plantations contained this pest, and the average number of trees infested was 48% (max100%). The survey suggests that these pests could be serious in young plantations.

Pine spittlebug damage

The pine spittlebug commonly occurs across the range of pine in Ontario. High, though localized populations are frequently reported on eastern white pine, and where this occurs the pine spittlebug is capable of injury (Martineau1984). Consecutive years of heavy infestations may result in twig, branch and whole tree mortality (Rose et al. 1999). White Pine Blister Rust Cronartium ribicola J.C. Fisher Throughout the survey, trees were recorded as being severely affected if the disease was present on the main stem, or if more than 25% of the branches were infected. The disease was recorded in 52% of the eastern white pine plantations surveyed. In the <2 m height class, 46% of the plantations had an average of 7% (maximum 51%) of the trees affected, of which 5%, (maximum16%) were rated as severe. In the 2-6 m height class, 62% of the plantings were infected, averaging 4% (maximum 13%) of the trees at each location, of which 3%, (maximum 11%), were rated as severe. In the > 6 m class, 48% of the plantations contained the disease, with an average of 4% of trees (maximum 15%), with 2%, (maximum 7%) being severe. White pine blister rust is a very serious pest of eastern white pine and along with weevil attacks, is often the limiting factor in growing white pine. The disease affects trees of all ages and sizes and kills all parts of the host that are distal to the canker. It can kill seedlings and juvenile trees very quickly. The disease increases and spreads slowly at first through a plantation, then rapidly (Lavallee 1992b).

26

Young white pine killed by blister rust

Blister rust is climatically sensitive, and on this basis hazard zones have been developed (Gross 1985). In a high hazard zone this disease is very difficult to control but can be managed through a silvicultural approach. Infected branches should be pruned and severely infected trees should be completely removed from the stand. Destroying and removing the alternate host, Ribes spp., within 300 m of eastern white pine plantations is strongly recommended (Myren 1994). Exercising silvicultural practices such as pruning of young trees or use of shelterbelts will greatly reduce the impact of this disease. Plant resistant varieties of white pine when possible, and avoid planting areas where the alternate host is abundant (Myren 1994). Armillaria Root Rot Armillaria spp.

Armillaria root rotcommonly occurs in pine plantations and natural forested areas throughout Ontario. In the surveys, root rot affected 9% of the eastern white pine plantations. In the < 2 m height class 9% of the plantations were found affected (Figure 3) with an average of 3%, (maximum 7%), of the trees killed (Table 4). In the 2-6 m height class, the percentage of infected plantations increased to 15%, with only 1% of trees affected. In the > 6 m height class only 4% of the plantations were affected, with 1% of the trees in these plantations attacked by the disease. Armillaria root rot is the most serious root disease in Ontario, capable of decaying and killing both deciduous and coniferous trees and shrubs in natural forests and plantations in all age classes, although pines are considered less susceptible than spruce species (Whitney 1988). Pine Needle Diseases: Sooty Mold, Capnodium spp. Needle Cast, Lophodemrium spp. Dipoldia Tip Blight, Sphaeropsis sapinea (Fr.) Dyko & B. Sutton During the surveys of eastern white pine plantations no specific needle disease was evaluated. Any foliar problem that was encountered was recorded along with its damage level. Overall, 21% of the eastern white pine plantations examined were affected by a foliage diseases, with all height classes being affected (Figure 3). In the < 2m height class, 23% of the plantations were affected, with damage occurring on an average of 10% (maximum 30%) of the trees, and resulting in 18% (maximum 37%) defoliation (Table 4). In the 2-6 m height class, 28% of the plantations were affected, and the average incidence

27

increased to 17% (maximum 53%), with corresponding defoliation levels of 17%. In the > 6 m height class, 11% of plantations were affected, with 11% of the trees damaged (maximum 32%). The defoliation levels increased to 25%. Weather generally plays a significant role in the abundance of needle diseases and the damage they cause; cool moist condition result in increased disease. The higher levels of defoliation in larger stands were likely the result of higher humidity levels in a closed canopy. Heavy defoliation by needle diseases in Ontario is not normal..

28

1 2 3 4 5 6 70

10

20

30

40

50

60

70

Perc

ent s

tand

s af

fect

ed

Tota l T - L M - S

1 = W hite pine weevil, 2 = P ine bark adelgid, 3 = E uropean pine shoot borer, 4 = P ine spittle bug,5 = W hite pine blister rust, 6 = P ine needle diseases, 7 = A rm illaria root rot

Height class < 2m

1 2 3 4 5 6 70

10

20

30

40

50

60

70

Perc

ent s

tand

s af

fect

ed

Total T - L M - S

1 = W hite pine weevil, 2 = P ine bark adelgid, 3 = European pine shoot borer, 4 = P ine spittle bug,5 = W hite pine blister rust, 6 = P ine needle d iseases, 7 = Arm illaria root rot

Height class 2 - 6m

1 2 3 4 5 6 70

10

20

30

40

50

60

70

Perc

ent s

tand

s af

fect

ed

Tota l T - L M - S

1 = W hite pine weevil, 2 = P ine bark adelgid, 3 = E uropean pine shoot borer, 4 = P ine spittle bug,5 = W hite pine blister rust, 6 = P ine needle diseases, 7 = A rm illaria root rot

Height class > 6m

Figure 3. Percent of eastern white pine plantations affected by various pests in three height classes, < 2m, 2-6m, and > 6m.

29

PESTS OF WHITE SPRUCE Eastern Spruce budworm Choristoneura fumiferana Clemens. The spruce budworm was detected in about 50% of all spruce plantations surveyed (Figure 4). The incidence of budworm in affected plantations increased with tree size, as did average defoliation (Table 5). In plantations > 6m, an average of 64% (maximum 100%) of trees showed budworm damage with mean defoliation at 19%. . The relationship between height and susceptibility to budworm is accepted but not well understood. However, Mattson et al. (1991) suggested that stands of larger trees might provide a more suitable physical environment for the insect.

Eastern spruce budworm damage

The eastern spruce budworm is the most destructive insect pest of white spruce in Ontario. Throughout the entire period of the survey, a major infestation of the eastern spruce budworm occurred across much of the province. This extensive infestation resulted in the loss of millions of cubic metres of spruce. Moderate-to-severe defoliation will result in overall loss of vigour and growth (Howse 1981). Top kill occurs after three consecutive years of severe defoliation (>75%), and whole tree

mortality will occur following five years (USDA Forest Service 1985). Numerous parasites, predators, birds, mites, spiders, and several pathogenic organisms help control the eastern spruce budworm naturally but do not prevent outbreaks. The most important natural controlling factor is weather. Late spring frosts often kill large numbers of early instar larvae (Martineau 1984). During periods of severe outbreaks the application of the biological insecticide, Bacillus thuringiensis has proven to be effective (Rose and Lindquist 1994). Spruce Coneworm (Dioryctria reniculelloides Matuura & Munroe) Spruce coneworm was associated with plantations of all height classes, but only in 10-20% of the plantations surveyed (Figure 4). In affected plantations relatively few trees < 6m in height were damaged by this insect (Table 5). Within affected plantations the incidence of coneworm was generally low (Figure 4, Table 5). The highest levels of coneworm occurred in 2-6 m plantations, where an average of 38% of the trees (Maximum 100%) were infested. Damage in all plantations was limited to light levels over the duration of the survey.

Spruce coneworm damage

30

The damage caused by coneworm feeding on foliage is not distinguishable from that of eastern spruce budworm when the two occur on the same tree. Generally though, spruce coneworm consumes less foliage and has less effect on host vigour than spruce budworm (Ives and Wong 1988) and is reported to favour cones as a food source (Hedlin et al. 1980). The spruce cone worm attacks both the cones and the foliage of the white spruce trees and during certain years heavy cone losses occur (USDA Forest Service 1985). There are a number of different species of parasites that readily attack the spruce cone worm (Martineau 1984). In a high-value plantation where cone production is important, the collecting and burning of infested cones in the late fall or early winter would provide some level of protection. A stomach insecticide may be applied to the foliage in July when the larvae are actively feeding (Martineau 1984). White Pine Weevil Pissodes strobi Peck White pine weevil was found affecting about 20% of white spruce plantations <6m in height, and only about 3% of plantations >6m in height (Figure 4). Incidence of this insect in affected plantations was generally very low, particularly in plantations >6m in height (Table 5). In smaller trees (<6m) the incidence averaged about 2% (Table 5). Most published accounts of this insect concern its association with white pine. The impact of weevil on eastern spruce species is unclear, although in western Canada this insect is a serious pest of white spruce (Taylor et al. 1991). The surveys note the presence of the insect in

white spruce plantations but at much lower levels than are seen in white pine plantations, at least during the period of the survey. The data does suggest that weevil on spruce is less prevalent on trees over 6 m in height, consistent with the general literature on weevil on white pine. Yellowheaded spruce sawfly Pikonema alaskensis Roh. The yellowheaded spruce sawfly was observed in all height classes (Figure 4). About 30% of all plantations <6m in height were affected. In affected plantations, <2m in height, sawfly attacked an average of 19% (maximum 93%) of the trees (Table 5). In spite of the high incidence in some plantations only light defoliation was recorded during the survey (Table 5).

Yellowheaded spruce sawfly damage The yellowheaded spruce sawfly is a serious defoliator of young, open grown white spruce. Heavy defoliation can result in branch mortality and will cause considerable decreases in radial growth (Martineau 1984). Repeated severe defoliation by this insect will result in loss of tree vigour and mortality. The

31

insect is known to concentrate its attack on previously defoliated trees, increasing the likelihood of damage (Ives and Wong 1988). Seedlings may be completely denuded of foliage and die in a single year. Trees less than 2 m in height may be killed following three or four consecutive years of heavy defoliation (USDA Forest Service 1985). Spruce Bud moth Zeiraphera canadensis Mutuura & Freeman The spruce bud moth was present in a significant number of plantations in all three height classes (Figure 4). Within affected plantations, the incidence of the insect increased with tree height (Table 5). In plantations >6m in height, an average of 44% (maximum 100%) of trees were attacked by the bud moth (Table 5), in plantations <2m and 2-6m 13% and 30% of the trees, respectively were attacked. However in all height classes maximum values ranged between 85 and 100%. This apparent relationship with height is in contrast to that reported by Turgeon (1992), who suggested that budmoth populations typically decline with tree height. Pure stands of white spruce are known to be susceptible although several years of severe defoliation are necessary for any impact on tree growth (Carroll et al. 1993). Feeding damage caused by the spruce bud moth routinely deforms the elongating shoots on young, open-grown white spruce. Damage is usually heaviest on apical shoots and particularly on the terminal or leader growth, which affects the overall form of the tree (Martineau 1984). Numerous parasites and predators attack and feed upon the larvae of this bud moth, but chemical control may be required to control damaging population

levels. A typical contact insecticide, applied at high pressure, as the buds begin to elongate, has proven to be an effective control of this pest (Rose and Lindquist 1994).

Spruce budmoth damage

Armillaria Armillaria spp. Over the study period, armillaria was found affecting a small percentage of white spruce plantations of all height classes (Figure 4). Mortality caused by root rot was most frequently encountered in plantations <2m (Figure 4). But in all cases, armillaria induced mortality was between 1-2% (Table 5). The range of values for annual mortality is similar to that found by Whitney (1988), who reported an average mortality rate of 1.4% on white spruce. However, mortality induced by armillaria is only part of the issue, as the fungus infects a high proportion of trees without killing them outright. Livingston (1990) reported that in 27 young spruce plantations in Maine, 89% were infected with armillaria, although in most plantations less than 1% were recently killed by the disease. Similarly, Wiensczyk et al. (1996) surveyed forty, 5-to-15 year old black spruce plantations in Northwestern Ontario and found infection in every site with levels

32

ranging from less than one to 32%; cumulative mortality on these sites ranged between 0 and 10%. Armillaria is a serious problem in spruce plantations (Whitney 1988) but its impact in an individual plantation is related to a number of factors including the strain of the fungus, host vigour and environmental stress factors (Whitney and Dumas 1994). The disease often becomes parasitic when the overall vigour of the host declines as a result unfavourable environmental conditions, particularly drought. Armillaria induced mortality may appear as single scattered trees or as small, circular pockets, especially in mono cultural plantation. Because of weakened root systems, heavily infected trees experience radial growth loss, butt rot, and are prone to wind throw (USDA Forest Service 1979). Our results and others suggest that armillaria is a common and chronic problem in spruce plantations and while mortality is normally at low levels, the potential for severe damage does exist. Spruce needle rust Chrysomyxa Ledicola Lagh. C. Ledi d By Needle rust was observed in about one third of surveyed spruce plantations, but was most common in plantations <6m (Figure 4). In affected plantations the incidence of the disease was high on all height classes (Table 5). In plantations <2m, and 2-6m in height, an average of 57% and 49% (maximum 100%) of trees respectively were infected. This disease is common in Ontario and can be found over large areas where black or white spruce is present and when weather is conducive to infection. Although defoliation was found at low levels during this survey, serious defoliation

can occur during some years. In 1994, foliar damage up to 40% was reported on white spruce in northeastern Ontario (Jones et al. 1995). Spruce needle rust infects and kills current year�s needles, and occasionally infects cones. Little is known about the impact on trees caused by infection of needle rust. However it is assumed that repeated years of heavy infection can result in a reduced growth rate (Myren 1994). However, this data and additional surveys indicate that infection usually occurs at low levels. Removal of the alternate host, Labrador tea, Ledum spp., is an effective natural control of this fungus (Ziller 1974). Spruce cone rust Chrysomyxa pirolata Wint. Cone rust was found in only a small percentage of white spruce plantations >2 m in height (Figure 4). In the 2-6 m and > 6m classes, incidence of infected trees was 16% and 8.5% respectively (Table 5). This disease is a serious pest when cone crops are considered, but is insignificant in terms of overall tree health. High levels of infection are rare in Ontario, but do occur periodically (McPherson et al. 1982). Spruce cone rust causes malformation, premature opening, reduced seed production, and decreased viability of seeds in white spruce cones. In certain years, the fungus causes severe damage to cone and seed production over very large areas (Myren 1994). Controlling or removing the alternate host, wintergreen, Pyrola spp., is an effective natural control of this cone rust disease (Ziller 1974).

33

Spruce cone rust

Frost: Frost damage was evident in about 50% of spruce plantations < 6 M in height, but was detected in fewer white and black spruce plantations >6m (Figure 4). The average incidence of frost was also much higher in plantations <6m, with about 50% of the trees being affected in both height classes (Table 5). Stathers (1989) notes that a tall closed canopy reduces the risk of frost by reducing heat loss from the ground. However, even though the frequency of occurrence was lower in the taller plantations, an average of 30% of trees in affected plantations showed evidence of frost (Table 5). Frost damage generally occurs on new foliage. The occurrence and extent of damage are usually related to exposure and topography (Lavallee 1992c). Site selection and avoidance of depressions, north-facing slopes and flat plateaus where reduced air flow is likely, are simple control measures, when frost damage to young plantations is a concern (Stathers 1989).

34

1 2 3 4 5 6 7 8 9 10 11 120

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1 = S pruce budw orm , 2 = S pruce cone w orm , 3 = S pruce bud m oth , 4 = W h ite p ine w eev il, 5 = Y e llow headed sp ruce saw fly, 6 = S pruce need le rust, 7 = A rm illa ria roo t ro t, 8 = S pruce cone rus t,9 = S pruce b room rus t, 10 = E as te rn dw arf m is tle toe , 11 = F ros t, 12 = C h lo ros is

1 2 3 4 5 6 7 8 9 10 11 120

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20

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1 2 3 4 5 6 7 8 9 10 11 120

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Figure 4. Percent of white spruce plantations affected by various pests in three height classes, < 2m, 2-6m, and >6m.

35

PESTS OF BLACK SPRUCE Eastern Spruce budworm Choristoneura fumiferana Clemens. The spruce budworm was found in about 50% of all plantations (Figure 5). The insect was found in all height classes but was most prevalent in plantations >6m in height, where 73% of all trees in affected plantations sustained defoliation by budworm (Table 6). Average defoliation values were relatively low in all height classes but greatest (16%) in plantations >6m. The eastern spruce budworm is a destructive insect pest of black spruce in Ontario. Throughout the entire period that black spruce plantations were surveyed a major infestation of the eastern spruce budworm occurred across much of the province. This extensive infestation resulted in the loss of millions of cubic metres of spruce/fir forest. Moderate-to-severe defoliation will result in overall loss of vigour and growth (Howse 1981). However, pure stands of black spruce (lowland or plantation) generally survive budworm outbreaks, but a severe attack will result in decreased growth and can predispose the trees to secondary pests (Howse 1981). The data from this survey indicates the increased likelihood of attack by budworm with increased height. Spruce Coneworm Dioryctria reniculelloides, Matuura & Munroe The spruce coneworm was identified in about 10% of visited plantations (Figure 5). The insect was found in all height classes but frequency was very low. The highest populations were found in 2-6m plantations, where 17% of

plantations were affected (Figure 5). In these plantations 6.3 % (maximum 23.0%) of trees were attacked by this insect (Table 6). Damage caused by the coneworm is indistinguishable from the spruce budworm with the two insects often feeding on the same tree. However, the spruce coneworm consumes less foliage and has less effect on host vigour than the budworm (Ives and Wong 1988) and favours cones as a food source (Hedlin et al. 1980). The spruce coneworm attacks both the cones and the foliage of black spruce trees and during certain years it will take a heavy toll on cones (USDA Forest Service 1985). There are a number of different species of parasites that readily attack the spruce cone worm (Martineau 1984). It would not be practical in a forest setting, but in a high-value plantation, the collecting and burning of infested cones in the late fall or early winter would provide some level of protection. A stomach insecticide may be applied to the foliage in July when the larvae are actively feeding (Martineau 1984). Yellowheaded spruce sawfly (Pikonema alaskensis Roh.) The yellowheaded spruce sawfly was observed ina limited number of black spruce plantations (Figure 5), in all height classes. In the taller plantations (>6m), an average of 21% (maximum 60%) of the trees were damaged by sawfly. In plantations <2m in height, 15.2 % of the stands were affected, and 48% of the trees were damaged in one surveyed plantation (Table 6). In spite of the high incidence in some plantations only trace to light levels of damage were recorded during the survey. However repeated severe defoliation by this insect

36

will result in loss of tree vigour and mortality. The insect is a pest of black, white and Engelmann spruce, and is known to concentrate its attack on previously defoliated trees, increasing the likelihood of damage (Ives and Wong 1988). Open grown trees are most susceptible to attack. Whitespotted sawyer beetle Monochamus scutellatus Say The sawyer beetle was found only on younger trees <2m in height (Figure 5). This beetle was found in only one plantation, and here, only 4.0% of trees were damaged (Rose and Lindquist 1994). While this insect is not usually considered a problem of young plantations, it was included in this survey due to the high populations evident in northern Ontario in the late 1970s (seeThomson and Sajan 1978).. The beetle, which usually feeds, on young twigs can cause serious defoliation along the edges of conifer stands White Pine Weevil (Pissodes strobi, Peck) White pine weevil was found affecting abut 35% of plantations <6m in height, and only about 3%of those >6m (Figure 5). Incidence of this insect in affected plantations was generally very low, particularly in those >6m in height (Table 6). In smaller trees (<6m) the incidence averaged about 2% (Table 6). In plantations between 2-6 m up to 19.3 % of trees were affected. The maximum incidence observed in affected plantations of < 2 m was 9.3 %, and 2.6% in stands over 6 m. The white pine weevil is a serious pest problem of young white spruce plantations but the impact it has on black

spruce is unclear. The survey suggests that the white pine weevil is present at potentially damaging levels in black spruce plantations, especially < 6 m in height. However the survey does not show whether individual trees were attacked in more than one year. All size classes of trees are attacked, but open-grown trees less than 8 m in height are most affected (Martineau 1984). Weather also causes fluctuations in populations of this weevil (Sullivan 1961). During years of high populations, control measures should be considered, especially in the 2-6 m height class. If the weevil does exist at high levels in a young plantation then the physical removal of infested shoots and leaders is a very effective control and should also be considered ( Rose et al. 1999). Armillaria root rot Armillaria spp. Armillaria was present in all height classes of surveyed plantations, but was most common in plantations <2m in height (Figure 5). Within affected plantations, mortality attributed to armillaria averaged 1%, with up to 2% being evident in a <2m plantation (Table 6). Black spruce >6m were least affected with only 4% of stands damaged (Figure 5), and average mortality of <1%. Whitney (1988) reported average mortality rates of between 0.1 and 4.8% attributable to armillaria in black spruce plantations. The difficulty with dealing with below ground organisms is assessing their presence in the absence of mortality. In the case of armillaria the fungus is often present over a broad area. Livingston (1990) reported that in 27 young spruce plantations in Maine, 89% of the trees were infected with armillaria, although in most plantations less than 1% were recently killed by the

37

disease. Similarly, Wiensczyk et al. (1996) surveyed forty, 5-to-15 year old black spruce plantations in Northwestern Ontario, and found infection in every site with levels ranging from less than one to 32%. These authors did not report on current mortality, but cumulative mortality on these sites ranged between 0 and 10%. Our results and others suggest that although the armillaria is a common and chronic problem in spruce plantations, mortality is normally at low levels, although the potential for serious damage always exists. Our survey results also suggest that mortality is more common in the youngest trees. However, Whitney (1995) suggests that armillaria is even more prevalent in older black spruce (90-130 years), which should be taken into consideration in forest management planning Spruce needle rust Chrysomyxa Ledicola Lagh., C. Ledi Alb. & Schwein Needle rust was observed in black spruce plantations of all height classes, affecting close to 50% of plantations surveyed (Figure 5). In affected plantations the incidence of the disease was high on all height classes with about 50% of all trees being affected over the duration of the survey (Table 6). However, the level of damage, as indicated by defoliation was low on average and similar between height classes averaging between 3.4 and 6.5%. This rust has been poorly studied in terms of its impact on trees. However, repeated years of heavy infection possible results in a reduced growth rate (Myren 1994). In one recent survey (Ingram et al.1992), 80% of black spruce at 27 locations across Northeast Ontario were infected. Defoliation levels of 99% have been

recorded in Ontario due to this disease. However, this study and additional surveys indicate that infection usually occurs at low levels.

Spruce needle rust damage Spruce broom rust Chrysomyxa arctostaphyli Dietel This disease was only observed in trees >6m in height, and only in less than 5% of surveyed plantations (Figure 5). Within affected plantations (Table 6), the disease was only found at low levels (0.7%). This disease is seldom considered a problem, but along with eastern dwarf mistletoe Arceuthobium pusillum Peck, which causes similar brooming, it can be of local concern. Both diseases can spread within an affected stand, and while either seldom causes tree mortality, they often result in stem breakage, resulting in increased stem decay (Myren 1994). Spruce cone rust Chrysomyxa pirolata Wint. Cone rust was found in all white spruce plantations of <6 m (Figure 5). The rust was not evident in plantations <2m, which do not usually bear cones. About 7% of 2-6m plantations were infected, and about 4.5% of the trees in these plantations (maximum 8.0%) showed

38

evidence of rust. Less than 5% of the plantations >6m had cone rust but in these plantations about 8% of the trees were infected (maximum16%) (Table 6). This disease is considered as a serious pest when cone crops are considered, but is insignificant in terms of overall tree health. High levels of infection are rare in Ontario, but do occur periodically (McPherson et al. 1982). Frost Frost damage was commonly observed in plantations of all height classes, however damage was more commonly observed in plantations <6m in height (Figure 5). Within affected plantations the incidence of frost was high in all height classes with 50-60% of trees being affected (Table 6). In individual plantations up to 100% of black spruce could be damaged by frost (Table 6). Results from this survey were very similar to the results for the survey of white spruce even though white spruce is considered more susceptible (Lavallee 1992c)

Frost damage

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1 2 3 4 5 6 7 8 9 10 110

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H eight c lass < 2m

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Figure 5. Percent of black spruce plantations affected by various pests in three height classes, < 2m, 2-6m, and >6

40

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Canada. Dep. Environ., Can. For. Serv. Victoria, B.C. Publ. No. 1329. 272 p.

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Table 2. Average incidence of pest and defoliation, by height class, in affected red pine plantations. Height class <2m 2-6m >6m Incidence Defoliation Incidence Defoliation Incidence Defoliation Mean Max. Mean Mean Max. Mean Mean Max. Mean Pest (%) (%) (%) (%) (%) (%) (%) (%) (%) Pine false webworm 7.7 3.1 3.2 31.6 73.0 8.5 2.0 2.0 1.0 Redheaded pine sawfly 1.7 4.0 2.21 2.5 9.0 NA 0.0 0.0 NA Red pine sawfly 4.2 7.3 1.31 1.9 6.0 NA 1.7 2.0 NA European pine shoot moth 21.3 78.6 NA 1.6 3.0 NA 0.0 0.0 NA Armillaria root rot 3.2 8.0 NA 0.0 0.0 NA 2.0 2.0 NA Pine needle rust 40.5 100.0 5.4 31.5 88.0 3.2 31.0 60.0 21.5 Scleroderris canker 32.3 84.7 NA 34.0 69.3 NA 7.0 7.0 NA Pine needle cast 4.6 8.0 0.9 7.1 20.0 3.0 0.0 0.0 0.0 1Average number of sawfly colonies per infested tree Table 3. Average incidence of pest and defoliation, by height class, in affected jack pine plantations. Height class <2m 2-6m >6m Incidence Defoliation Incidence Defoliation Incidence Defoliation Mean Max. Mean Mean Max. Mean Mean Max. Mean Pest (%) (%) (%) (%) (%) (%) (%) (%) (%) Jack pine budworm 1.5 95.3 1.5 22.1 100.0 1.7 58.4 100.0 5.8 White pine weevil1 4.0 14.7 NA 3.4 14.1 NA 1.4 2.0 NA Eastern pine shoot borer1 2.8 9.3 NA 2.9 11.0 NA 2.1 5.3 NA Jack pine tip beetle1 1.5 4.0 NA 2.8 10.0 NA 0.9 2.7 NA Jack pine sawfly2 0.7 1.3 NA 1.4 5.0 NA 0.9 1.3 NA Armillaria root rot 1.0 3.3 NA 0.8 3.0 NA 0.7 0.7 NA Scleroderris canker 21.0 59.3 NA 17.9 75.3 NA 1.3 1.3 NA Pine needle rust 27.4 100.0 3.7 39.5 100.0 4.1 42.1 81.0 1.4 Pine needle cast 1 9.6 77.3 16.6 12.8 70.4 4.2 35.3 100.0 14.6 Western gall rust 6.4 32.6 NA 12.1 80.0 NA 21.3 85.0 NA Stem rusts 1.6 7.2 NA 1.8 10.4 NA 6.2 15.3 NA 1 % of trees with leader damage 2Average number of sawfly colonies per infested tree

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Table 4. Average incidence of pest and defoliation, by height class, in affected white pine plantations. Height class <2m 2-6m >6m Incidence Defoliation Incidence Defoliation Incidence Defoliation Mean Max. Mean Mean Max. Mean Mean Max. Mean Pest (%) (%) (%) (%) (%) (%) (%) (%) (%) White pine weevil 7.5 29.3 NA 11.6 60.0 NA 5.9 33.3 NA Eastern pine shoot borer 2.8 12.7 NA 2.6 6.0 NA 7.6 22.0 NA Pine bark adelgid 10.3 53.0 NA 9.7 32.0 NA 32.4 100.0 NA Pine spittlebug 9.7 76.0 NA 16.0 100.0 NA 48.2 100.0 NA White pine blister rust 6.6 50.7 NA 4.4 13.3 NA 3.5 15.3 NA Armillaria root rot 2.5 7.3 NA 1.1 1.5 NA 0.7 0.7 NA Pine needle diseases 10.0 30.0 18.1 16.9 53.3 17.4 11.0 32.7 24.8 Table 5. Average incidence of pest and defoliation, by height class, in affected white spruce plantations. Height class <2m 2-6m >6m Incidence Defoliation Incidence Defoliation Incidence Defoliation Mean Max. Mean Mean Max. Mean Mean Max. Mean Pest (%) (%) (%) (%) (%) (%) (%) (%) (%) Spruce budworm 31.9 100.0 6.6 43.8 100.0 6.1 64.3 100.0 19.1 Spruce cone worm 1.4 4.0 NA 9.6 82.0 NA 37.9 100.0 NA White pine weevil 1.9 6.0 NA 2.3 7.3 NA 1.1 1.3 NA Yellowheaded spruce sawfly 19.3 93.3 5.2 7.0 29.0 2.1 5.4 17.3 1.4 Spruce bud moth 13.3 85.0 NA 30.5 100.0 NA 43.8 100.0 NA Armillaria root rot 0.8 1.3 NA 1.6 2.0 NA 0.8 1.0 NA Spruce needle rust 56.8 100.0 4.0 49.2 100.0 4.0 32.6 100.0 1.0 Spruce cone rust 0.0 0.0 NA 15.8 37.0 NA 8.5 16.0 NA Frost 49.5 100.0 5.7 52.4 100.0 5.3 29.7 93.0 2.2

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Table 6. Average incidence of pest and defoliation, by height class, in affected black spruce plantations. Height class <2m 2-6m >6m Incidence Defoliation Incidence Defoliation Incidence Defoliation Mean Max. Mean Mean Max. Mean Mean Max. Mean Pest (%) (%) (%) (%) (%) (%) (%) (%) (%) Spruce budworm 42.9 100.0 2.1 42.9 100.0 4.6 73.3 100.0 15.9 Spruce coneworm 3.2 7.0 NA 6.4 23.0 NA 4.5 8.0 NA Yellowheaded spruce sawfly 10.1 48.0 3.9 1.5 3.3 1.8 21.5 60.0 1.5 White pine weevil 2.8 9.3 NA 3.5 19.3 NA 1.3 2.6 NA White spotted sawyer beetle 4.0 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Armillaria root rot 1.0 2.0 NA 1.1 1.3 NA 0.7 0.7 NA Spruce needle rust 56.6 100.0 6.5 50.5 100.0 3.5 42.8 100.0 3.4 Spruce broom rust 0.0 0.0 NA 0.0 0.0 NA 0.7 0.7 NA Spruce cone rust 0.0 0.0 NA 4.5 8.0 NA 8.0 16.0 NA Frost 49.1 100.0 8.6 51.8 100.0 4.3 62.2 100.0 7.4

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General Considerations for Forest Management of the Major Insects and Diseases by Tree Species Working Group The accessibility of a forest stand, its productivity and ecological conditions, as well as the prevailing ecological, social and economic values determine in large measure the intensity of forest management and consequently the importance of insect and disease pests. The most logical sites for direct enhanced forest productivity are on accessible sites with potential for high productivity. The purpose of this section is to introduce the major insects and diseases of black and white spruce; jack, red and white pine; and aspen, and to present some general forest management guidelines. More detailed information is provided in the section describing each insect and disease. Black spruce The spruce budworm (Choristoneura fumiferana), the yellowheaded spruce sawfly (Pikonema alaskensis) and the white pine weevil (Pissodes strobi) are occasionally pests of black spruce. During an outbreak of spruce budworm, upland black spruce growing with balsam fir can suffer some growth loss. Open grown spruce are susceptible to the weevil and sawfly, but they are only infrequently a serious problem on these trees. Standard silvicultural practices of planting, spacing, and stand improvement seldom result in serious insect problems and generally, silvicultural intervention is rarely needed or practical for black spruce. Black spruce has few significant disease problems. Numerous minor problems such as needle rusts and mistletoes exist, but they normally cause minimal impact in terms of

mortality and growth loss. Root and butt rots caused by Armillaria (Armillaria spp.) and tomentosus root rot (Inonotus tomentosus) are common in black spruce stands. They can cause significant mortality to young trees in newly established stands and result in poorly stocked stands or ones with large openings. Typically, these rots are more serious on mature trees over in age and are a major contributing factor growth loss and to blow down. Tomentosus, while affecting all conifer species is most serious on spruces more than 30 years of age, particularly on well-drained sites. Early harvest should be considered if the disease is well established. The area should be replanted with a less susceptible pine species if the site is appropriate. White spruce The major insect pests of white spruce are the spruce budworm (Choristoneura fumiferana), the yellowheaded spruce sawfly (Pikonema alaskensis) and the white pine weevil (Pissodes strobi). Spruce budworm is particularly troublesome where white spruce is mixed with balsam fir. Both the weevil and the sawfly are pests of young open-grown trees. Establishing closely spaced plantations, promoting rapid tree growth, planting white spruce under a hardwood overstory, or delaying stand spacing until trees are at least 20 years old and/or 5 m tall will help reduce the impact of the white pine weevil and the yellowheaded spruce sawfly. White spruce can tolerate several years of defoliation by the spruce budworm. Management of the spruce budworm on white spruce may require the reduction or removal of mature balsam fir in mixed conifer stands, breaking up large areas of mature forests and avoiding creating large single species plantations. Presalvage of forest stands as a pre-emptive measure should be considered where white spruce is most vulnerable to damage.

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Armillaria root rot (Armillaria spp.) and Tomentosus root rot (Inonotus tomentosus) can be problems for young white spruce that are planted on former hardwood sites. Direct control procedures for root rots are usually neither practical nor economic. Avoidance and early detection are the best strategies in plantation management. Stem decays are normally a problem with older trees in natural forests. However, damage caused to young and semi-mature trees during thinning operations makes pre-mature decay increasingly likely in managed stands. Jack pine The jack pine budworm (Choristoneura pinus) and the white pine weevil (Pissodes strobi) are the most serious insect pests of jack pine. Jack pine budworm is primarily a pest of mature jack pine, whereas the weevil is a pest of young open-grown stands. Bark beetles (Ips spp.) can be a problem where trees are stressed due to nutrient deficiencies, drought, wet soil, storm damage, defoliation caused by other insects or where logging or thinning have occurred recently and slash has not been removed. Root collar weevils are occasionally problems on extreme nitrogen-deficient soils, and where jack pine is established near scots pine stands. Silvicultural prescriptions for jack pine budworm are based on the need to develop jack pine stands that are less susceptible to attack and vulnerable to damage by reducing the abundance of male staminate flowers, and by promoting tree and stand vigour. Prescriptions to reduce stand susceptibility and vulnerability include managing jack pine to a predetermined rotation to avoid overmature stands, maintaining proper stocking, avoiding creating uneven-aged or two-storied stands and encouraging age class

and species diversity across the landscape. Managing the white pine weevil in jack pine stands is difficult because the option of providing overhead or side shade to a shade intolerant species like jack pine is not desirable. The alternative prescription of planting at a close spacing to promote crown closure and to delay thinning until trees have reached 5 m (if trees are grown for lumber production) is more feasible. The pine engraver beetle, Ips pini, is best managed by managing the slash left behind after logging. Slash less than 8 cm in diameter can be left because beetles seldom develop large populations in this material. Larger slash can be scattered to encourage rapid deterioration of the phloem or left in large deep piles to provide a food source and divert them away from standing trees left after thinning. Root collar weevils can become serious pests of young regeneration. Preventative measures include a delay in planting, removal of infested trees, planting jack pine with non-susceptible species, maintaining stocking standards and delaying thinning Scleroderris canker (Gremmeniella abientina) is a serious disease of jack pine but rarely kills trees over 2 m tall. It is typically a problem in frost pockets where it can result in significant mortality. Armillaria root rot (Armillaria spp) can be a problem on jack pine, but pines are normally more resistant to root rots. Dwarf mistltoe has proven to be a serious problem of jack pine and once established requires a significant effort for eradication. However, due to forest fire history this disease is presently absent from Ontario, even though it is prevalent in western Manitoba. Gall rust (Endocronartium harknessii) and stem rusts (Cronartium spp.) can also be serious problems in individual plantations. During thinning operations trees with serious levels of rust should be removed. These rusts are

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primarily a problem during the early years of plantation establishment. Red pine The major insect pest of red pine in the Great Lakes � St. Lawrence and transition boreal forest regions is the redheaded pine sawfly (Neodiprion lecontei). The sawfly is a problem in young open-grown stands. Bark beetles (Ips spp.) can be a problem where trees are stressed due to nutrient deficiencies, drought, wet soil, storm damage, defoliation caused by other insects or where logging or thinning have occurred recently and slash has not been removed. Root collar weevils are occasionally problems. Selecting the right site for a red pine plantation is probably the most important consideration for managing the sawfly because it is generally a problem where red pine is growing under stress. Other considerations include reducing competition from hardwoods, not planting red and jack pine in mixtures, and planting at a close spacing to encourage early crown closure. Managing the pine engraver beetle and root collar weevils in red pine is similar to that of jack pine. Scleroderris canker (Gremmeniella abientina), armillaria root rot (Armillaria spp.) and fomes root rot (Heterobasidium annosum) are the major diseases of red pine. Diplodia tip blight (Sphaeropis sapineai) and sirrococcus shoot blight (Sirococcus strobilinus) are occasionally problems. The European strain of Scleroderris is found in Canada. It can cause extensive mortality, but has been restricted to south central Ontario. Where it is a problem, the disease can be controlled through pruning until canopy closure is reached. Armillaria root rot can be a problem where red pine is established on sites where the disease was previously

common. Fomes root rot is the most significant disease problem of red pine and causes mortality to ages of pines. However, the disease is restricted by climate to southern Ontario and south western Quebec. Avoidance and early identification are the best control strategies for control of Fomes. Areas known to be affected should be harvested and replanted to hardwoods. More recently some success has been shown in the use of biological control agents. White pine The white pine weevil (Pissodes strobi) is the major insect problem of white pine. The weevil is a pest of open-grown trees, whereas the sawfly attacks both saplings and older trees, usually in open stands. There are two key approaches to managing the white pine weevil in white pine stands. The first is to provide overhead or side shade to reduce the amount of favourable habitat for the weevils. This can be accomplished through uniform shelterwood, underplanting or nurse crops. Providing side shade is a variant of the shelterwood system and is technically more difficult to use to manage the weevil. The other option is to grow white pine quickly to crown closure, again to reduce the amount of favourable habitat in a stand for the weevil. White pine blister rust (Cronartium ribicola) is the major disease problem of white pine. This introduced disease can cause mortality of young white pine, typically 8 m or less in height. Together with the white pine weevil this disease has severely hampered the regeneration of white pine. This disease can be managed by observing hazard zones and avoiding planting where infection is most likely. Silvicultural treatments such as pruning infected branches and growing under shelterwood help to reduce loss to the rust. If

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resistant stock is available, its use, together with increasing stand density in high hazard zones are also options. As always, the use of a non-host should be considered when rust limits the planting of white pine. As with other conifers, Armillaria root rot (Armillaria spp.) can be a problem for young white pine, although pines are generally less susceptible than spruces and armillaria is not usually limiting. Aspen The forest tent caterpillar (Malacosma disstria) and the large aspen tortrix (Choristoneura conflictana) are the major insect pests of aspen. Aspen stands that are at high risk to the forest tent caterpillar are found on poorly drained and drought-prone soils. Using forest management and silviculture for these insects is difficult and to date no prescriptions have been developed, except the suggestion to discourage fragmenting the forest into blocks of less than 100 hectares. The major diseases of aspen are Hypoxylon canker (Entoleuca mammatum), armillaria root rot and stem decays such as the white root rot (Phellinus tremulae). Hypoxylon canker is common in low-density stands and on stressed trees with stem and branch injuries. Trembling aspen is about five times more susceptible than large-tooth aspen to the canker. There is no direct control measure but removal of infected trees is recommended during stand improvement. The disease is also more prevalent in pure stands of aspen. White root rot is typically found in aspen over 40 years old and like all decays is more common in stands where wounding has occurred through storm damage or silvicultural practices. Reducing the length of stand rotation is probably the most effective way to manage the disease

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Forest Management Guidelines and Recommendations Insects Insect: Spruce budworm, Choristoneura fumiferana (Clemens) Distribution: The spruce budworm is found throughout Canada and the northern United States. It is a native insect, defoliating spruce-fir forests in eastern North America from Newfoundland southward to Virginia and westward through Canada�s boreal forests to British Columbia. Hosts: The principal hosts of spruce budworm are balsam fir, and white and red spruce. Mature balsam fir is the preferred host. Other conifers attacked include black spruce, eastern hemlock, tamarack, and eastern white pine particularly when these trees are growing along with the favoured food source (Rose et al. 1994). Host Damage: Spruce budworm larvae consume needles. In the spring, the newly emerged larvae mine needles of the previous year�s growth, unopened buds, and male flowers if present. As the larvae grow, they attack new needles and expanding buds, moving back to old needles as the supply of new growth diminishes. The larvae form feeding tunnels joining a few shoots together with silk. The top of the tree is the first to show damage, as transport of water and nutrients is affected. After heavy feeding, the tree appears �scorched�. Tree mortality and growth loss are functions of the timing, duration and intensity of defoliation. Attacks over consecutive years result in a decline in the tree�s capacity for production and storage of food and metabolites. Cone and seed mortality, losses in radial and height growth and rootlet death

occur. Stress and reduced vigour of trees will predispose them to attack by secondary insects and pathogens. Up to 90% reduction in tree growth as a result of loss of current year�s foliage has been reported (Steinman and MacLean 1994). Young trees are usually able to regenerate new rootlets and live, but

more mature trees often cannot and succumb. If more than 75% of the foliage is lost in a mature tree, death usually follows (Hudak and Raske 1982). Top-kill of balsam fir may begin after 2-3 years of heavy defoliation. Balsam fir mortality may begin after 3-5 years depending on tree vigour. All of these events can result in significant volume loss in stands. Budworm defoliation also results in seed loss, which can influence the composition of future stands (Schmitt et al. 1984). Other impacts, in addition to economic losses, include wildlife changes, increased vulnerability to forest fires and loss of recreation and aesthetics. Habitat: The spruce budworm is generally an insect of mature trees. Outbreaks frequently occur in areas with many mature and overmature stands (especially with large components of mature balsam fir) but can �spill-over� to younger trees. Studies of the population dynamics of spruce budworm have demonstrated that outbreak collapse is due to a variety of parasites and predators working together to increase larval mortality and reduce adult fecundity (Royama 1992).

Spruce budworm damage

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Forest Management Guidelines and Recommendations There is a large, diverse, and at times conflicting and contentious literature on the use of silviculture to manage the impact of the spruce budworm. During the late 1970s and 1980s there was a flurry of research activity and several valuable reviews and extension publications were produced. Flexner et al. (1983), Blum (1985), Blum and MacLean (1984, 1985) and MacLean (1996) have synthesized the extensive literature and provided sensible and practical guidelines to follow. Miller and Rusnock (1993) provide an interesting history of the use, discussion and criticism of silvicultural methods for spruce budworm. In the following sections, some general principles and caveats are provided as a background to the consideration of the use of silviculture to manage spruce budworm. General principles Before examining how silviculture might be used to mitigate spruce budworm damage, it is important that the concepts of susceptibility and vulnerability are understood. Susceptibility is the probability that a forest will be attacked. Susceptibility (to spruce budworm) may be quantified as the amount of defoliation that occurs (MacLean and MacKinnon 1997). Vulnerability is the probability that damage (e.g., relative growth rate and amount of mortality) will result from attack. The concepts are interrelated insofar as susceptibility determines the severity of attack and potential damage (Blum 1985). Differences in vulnerability among tree species, trees and stands are central to the use of silviculture to manage the spruce budworm.

Tree species, stand age, and hardwood content all influence the amount of mortality during a spruce budworm outbreak. Stand condition variables have been quite consistent over time and among geographic locations (Blum and MacLean 1984; MacLean 1996). Balsam fir is the most vulnerable to damage by the spruce budworm. Balsam fir usually dies after 5 to 7 years of severe attack and mortality in mature or overmature stands can reach 100%. Mortality of fir in immature stands or when mixed with spruce is generally less (MacLean 1980). White spruce is considered the next most vulnerable species. Because white spruce produces larger and more shoots than balsam fir (thus providing more food for larvae) damage is generally less severe than on balsam fir. Black spruce is less vulnerable than white spruce and balsam fir. This reduced vulnerability is primarily a function of later opening buds (typically 9 days after white spruce and 13 days after balsam fir) and because black spruce foliage is less suitable for young larvae (Greenbank 1963).

Spruce budworm induced mortality

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Stands with large amounts of mature or overmature fir tend to have consistently high mortality whereas immature spruce stands have low mortality (MacLean 1980, 1996). Although immature trees are less vulnerable than mature trees they are not immune to damage. The presence of staminate flowers on overmature dominant trees and those growing under unfavourable conditions increases the susceptibility and vulnerability to the spruce budworm (Greenbank 1963). Maturity is also accompanied by reduced growth and vigour of the trees. Stand size may be important because the mortality of dispersing larvae is likely lower in large continuous stands of mature forests. Vulnerability is further decreased as the proportion of non-host trees in the stand increases, or where hardwoods overtop a conifer understory. MacLean (1980) and Osawa et al. (1986) found that balsam fir forests with more than 20% hardwoods sustained less mortality than pure stands. Stands with at least 50% of the basal area in conifers are the most vulnerable (Flexner et al. 1983). If the spruce and fir are in a subordinate crown position, vulnerability is further increased. Site quality and growing conditions are also important. Generally trees and stands of low vigour and that show reduced growth rate and poor crown development are more vulnerable to damage. Several studies have shown that vulnerability tends to increase as stand density increases. This may be related to lack of vigour of the closely spaced trees or poorly developed foliage or decreased larval mortality during dispersal. But in a few cases, spaced stands can be severely defoliated and damaged (Blum and MacLean 1985), thus spacing of a stand isn�t always going to result in lowered vulnerability.

Until recently, abnormally wet or dry sites were considered more vulnerable to damage than more mesic sites. Balsam fir sustained, on average, 18% more mortality from spruce budworm on poorly drained than well-drained sites (Hix et al. 1987) and black spruce mortality was about 25% more on excessively dry than on poorly drained sites (Osawa 1989). Dupont et al. (1991)) found balsam fir mortality of 85, 75, 45 and 27% on xeric, hydric, mesic and subhygric drainage classes, respectively. On the other hand, MacLean and Ostaff (1989), Bergeron et al. (1995) and MacLean and MacKinnon (1997) did not find a strong or consistent relationship between soil drainage and budworm caused tree mortality, and recommended that the past emphasis on soil drainage class and surficial deposit as predictors of stand vulnerability be re-evaluated. In short, silvicultural prescriptions aimed at reducing the impact of spruce budworm include: 1) reducing the amount of balsam fir (especially mature and overmature trees) in a stand; 2) increasing the amount of less vulnerable host species (such as spruce) or non host species in a stand; 3) using a short rotation; and 4) maintaining vigourous trees with high growth rates. In broader terms, forest management would change the species composition of the forests, change the age class structure and change the spatial arrangement of stands. Achieving these goals should provide a general reduction in stand vulnerability for future budworm outbreaks. Caveats The recommendations for the use of silviculture to manage the spruce budworm have largely been based on retrospective analyses of outbreaks. Baskerville (1976), Blum and MacLean (1984, 1985) and several other authors, before and since, have cautioned that even the best of the

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suggestions to reduce vulnerability of a forest to spruce budworm have not been adequately tested over sufficient area, over sufficient time and over sufficient stand conditions to be considered anything but conceptual. Particularly vexing is the inability to predict the effectiveness of a treatment, that is, to establish a quantitative relationship between the treatment and the reduction of vulnerability. To quote Blum and MacLean (1984) �The real issue here is what specific actions, taken at what specific levels, at what specific times, in what specific forest and budworm conditions, will render future outbreaks less potent by what specific amounts.� Because spruce budworm outbreaks can occur over a large geographic area and last many years, and further, because we have many different forest types, stand, site and age conditions, climatic conditions, absolute population sizes, and many arrays of natural enemy complexes − not to mention different forest management objectives, policies and directives − it is easy to see why this is a daunting task. It would take 50-100 years to restructure the forest, and areas of more than 1 000 000 ha would require treatment (Baskerville 1976). In the absence of �hard data�, we can either simply wait until the research is complete or proceed on the basis that the concepts, although unproven, are logical and appear ecologically sound. Given the time frame involved and the significant damage the spruce budworm can cause, it is prudent not to wait but to attempt to potentially reduce the vulnerability and economic impact of the spruce budworm. One thing that seems virtually certain is that if we do nothing the spruce budworm will continue to be a major competitor with us for the forest resources. There are no simple solutions to the spruce budworm problem. Silviculture and forest management alone will not protect forests

from the spruce budworm because there are many other factors such as climate and natural enemies that are part of the population dynamics of this insect. The key to the use of silviculture is to reduce vulnerability (loss of growth, mortality) more than to reduce susceptibility (the probability of attack), which is largely unavoidable. Finally, it should be kept in mind that silviculture is only part of the pest management toolbox: this toolbox includes the use of direct control agents such as microbial and natural insecticides, and natural enemies. Including silviculture as part of the pest management plan can decrease the need for direct control with a longer time interval between direct control programs (Mott 1980); Dimond et al. 1984). As Baskerville (1975) noted �Since we cannot eliminate the problem [spruce budworm] we must be realistic in our expectations of forest management techniques and recognize that our aim is to compete with the budworm at a tolerable level of ecological disturbance.� Tactics The overall strategy in using the various tactics outlined below is to prevent outbreak populations of spruce budworm from developing. At one time, more than 50 years ago, the selection system of silviculture, which maintains an uneven-aged forest stand, was widely promoted as a method to manage the spruce budworm. Because this system of silviculture maintains an open almost mature crown with abundant sun, foliage and flowering, which are ideal for the spruce budworm, this method is no longer advocated for spruce budworm management (Baskerville 1975; 1976). In Ontario, black and white spruce are managed under an even-aged silvicultural system either through clearcutting or shelterwood (OMNR 1997, 1998). The tactics described below focus on individual stands. Because spruce budworm outbreaks can cover large geographic areas,

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regional strategies are essential but should be stand-oriented. On a regional basis, various combinations of these tactics should be considered where practical and appropriate. Plant less vulnerable species. Reforestation (or afforestation) of sites with species such as black spruce and to a lesser extent white spruce, which are less vulnerable than balsam fir, may be appropriate under certain ecological and economic scenarios. In essence, this is stand conversion. Establishing extensive areas of single species plantations may have some serious drawbacks. First, is the potential for increased vulnerability to other pests. White spruce plantations have had serious problems with the spruce budmoth (in New Brunswick and Quebec), the yellow-headed spruce sawfly, and the white pine weevil. White spruce is typically a mixedwood species and pure natural stands of white spruce are less common. Mixed-species plantations or growing white spruce under aspen can reduce insect problems. Black spruce on the other hand occurs naturally in �monocultures� and generally, plantations have fewer insect problems. Although much less vulnerable than balsam fir, black spruce is not immune to the budworm. Secondly, expensive and intensive site preparation and control of competing vegetation may be needed, especially on productive sites. Thirdly, the overall effect of stand conversion on local and regional wildlife habitat and food sources must be considered. Promote natural regeneration of less vulnerable species. Winter harvest stands mixed with aspen to encourage aspen reproduction to either convert it to an aspen stand or create a mixed stand. Aspen will provide protection for understory fir and spruce during an outbreak. Promote spruce regeneration through partial cutting, whenever possible. If shelterwood is to be

used, do so in stands with more than 50% spruce or non-host trees and where the residual trees are wind-firm and vigourous. If shelterwood is done during an outbreak, then the residual trees may need to be protected through direct control to reduce infestation of the developing regeneration. Reduce the amount of balsam fir in a stand. If natural regeneration is used to restock an area, it is frequently difficult to control the amount of balsam fir regeneration because it is an aggressive species that out-competes most species and tolerates a wide variety of growing conditions. One way to reduce the vulnerability of the stand is to preferentially remove balsam fir when thinning mixed fir-spruce or mixed fir-hardwood stands. Do not release balsam fir from a hardwood overstory, especially during a budworm outbreak or if one is anticipated in the near future. Batzer et al. (1987) observed that in balsam fir - aspen stands where all the aspen had been removed at age 36 or age 47, the balsam fir was much more vulnerable to damage than those stands thinned from above or below. Similarly, Crook et al. (1979) observed that thinning balsam fir in a mixed stand increased damage to balsam fir when some of the hardwoods (aspen and white birch) were removed but thinning balsam fir stands did not increase defoliation. Encourage mixed balsam fir-hardwood stand management. Recent work by Su et al. (1996) has demonstrated that as the amount of hardwood content in a hardwood-balsam fir stand increased, the amount of defoliation by spruce budworm decreased. Their work suggests that a hardwood content of 40% or more would substantially reduce losses during spruce budworm outbreaks. Although the underlying mechanism for this reduction remains unknown it is hypothesized that the greater amount of

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hardwood in the forest increases the diversity of populations of natural enemies such as parasitoids and birds. Needham et al. (1999) examined the relationship between hardwood and balsam fir content further and concluded that mixed stand management can potentially reduce balsam fir volume losses during a budworm outbreak. They also explore the application of these results under various forest management objectives such as reduction in pesticide use, production of balsam and/or hardwoods. It is of merit that they note again the complexities of managing forests for spruce budworm in context of the different forest management objectives, constraints, and opportunities superimposed by the variable landscape. Manage balsam fir stands on a rotation age of 40 to 60 years. Mature and overmature trees suffer the most severe damage, therefore shorten the rotation so that these species are less susceptible to attack and vulnerable to damage. A 40 to 60 year rotation would also reduce losses of volume due to rot and decay. Thinning of stands. Where pure stands of balsam fir are present, thinning should be considered to promote vigour and therefore reduce vulnerability. One potential drawback to thinning pure balsam fir stands has been the increase of damage from the balsam fir sawfly (Neodiprion abietis) (Piene et al. 2001). Although the spruce budworm was more damaging in spaced than in unspaced balsam fir stands, tree mortality was statistically the same (MacLean and Piene 1995). Piene and MacLean (1999) note that spacing did contribute to a rapid individual-tree recovery after spruce budworm defoliation. Break up areas of large areas of mature susceptible forests. Harvest by patch or block cuts to break up the continuity of large

areas of susceptible forests. This harvest method prevents stands from reaching maturity simultaneously over large areas. Higher dispersal losses of young larvae and adults should occur when the forest is fragmented because of the increased spatial diversity of different even-aged stands. Diversity in species compositions on a landscape scale is also required. For this to be a potentially effective tactic, the entire budworm-susceptible forest of a large region must be involved in such a program, which requires sustained and extensive co-ordination among different owners and political jurisdictions. Presalvage forests identified as the most vulnerable. This is a pre-emptive measure to dampen the impact of outbreaks and to use the wood before the budworm renders it useless. Vulnerable forests include those that are severely defoliated and those that are mature or overmature. Stands will need to be ranked according to their damage potential when scheduling the harvest. Stands with a large mature balsam fir component, growing on poor sites or ones with a high volume of sound wood should be harvested first. The publications by Dimond et al. (1984) and Blum and MacLean (1984) provide useful guidelines on how to set salvage priorities. Maintain a good road system. A good road system allows access to the sites in order to conduct stand improvement measures and also to pre-salvage or salvage the sites when needed. Some last words. The spruce budworm and the spruce-fir forests have evolved together in ecological succession whereby spruce-fir replaces spruce-fir and the budworm act as the causal agent for this replacement (MacLean 1982). Forest management alone will not be a

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panacea for managing the spruce budworm. Although it cannot be said with certainty that any of the above forest management guidelines will be effective, it is likely that planting less susceptible species and encouraging spatial age-class and spatial diversity over a large landscape will help reduce the impact of the spruce budworm, Well-managed and vigourous stands should respond well to direct control efforts that may be needed at some time in the rotation. Having a good portion of the forest in a less vulnerable condition should allow more time between control programs, decrease the need for control at the early stages of the infestation, and should allow more time for shifting salvage operations to the most vulnerable stands as the infestation progresses (Blum 1985). Forest management practices to reduce the impact of the spruce budworm must be considered a long-term strategy. References Baskerville, G.L. 1975. Spruce budworm:

The answer is forest management: Or is it? The Forestry Chronicle 51: 157-160

Baskerville, G.L. (ed). 1976. Report of the

task force for evaluation of budworm control alternatives. Prepared for the Cabinet Committee on Economic Development, Province of New Brunswick. Fredericton, N. B. New Brunswick Department of Natural Resources. 210 p.

Batzer, H.O.; Benzie, J.W.; Popp, M.P.

1987. Spruce budworm damage in aspen/balsam fir stands affected by cutting methods. Northern Journal of Applied Forestry 4: 73-75

Bergeron, Y.; Leduc, A.; Morin, H.; Joyal, C. 1995. Balsam fir mortality following the last spruce budworm outbreak in northwestern Quebec. Canadian Journal of Forest Research 25: 1375-1384

Blum, B.M. 1985. Appropriate silviculture.

pp 185-191 in Proceedings of the Symposium on Spruce-fir Management and Spruce Budworm. Society of American Foresters Region VI Technical Conference, April 24-26, 1984. Broomall, PA. USDA Forest Service, Northeastern Forest Experiment Station. General Technical Report. NE-99. 217 p.

Blum, B.M.; MacLean, D.A. 1984.

Silviculture, forest management and the spruce budworm. Chapter 6 in DM Schmitt, DG Grimble, JL Searcy; technical coordinators, Managing the Spruce Budworm in Eastern North America. Washington, D.C. U. S. Department of Agriculture Forest Service. Agriculture Handbook. 620.

Blum, B.M.; MacLean, D.A. 1985. Potential

silviculture, harvesting and salvage practices in eastern North America. pp 264-280 in Recent advances in spruce budworm research. Proceedings of the CANUSA Spruce budworms Research Symposium. Bangor, Maine, September 16-20, 1984. Ottawa, ON, Canadian Forestry Service, 527 p.

Crook, G.W.; Vezina, P.E.; Hardy, Y. 1979.

Susceptibility of balsam fir to spruce budworm defoliation as affected by thinning. Canadian Journal of Forest Research 9: 428-435

Dimond, J.B. ; Seymour, R.S. ; Mott, D.G.

1984. Planning insecticide application and timber harvesting in a spruce budworm epidemic. Washington, D. C.

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U.S. Department of Agriculture Forest Service. Agriculture Handbook 618. 29 p.

DuPont, A. ; Belanger, L. ; Bousquet, J.

1991. Relationships between balsam fir vulnerability to spruce budworm and ecological site conditions of fir stands in central Quebec. Canadian Journal of Forest Research 21: 1752-1759

Flexner, J.L.; Bassett, J.R.; Montgomery,

B.A.; Simmons, G.A.; Witter, J.A. 1983. Spruce-fir silviculture and the spruce budworm in the Lake States. Ann Arbour, Michigan. Michigan Cooperative Forest Management Program, University of Michigan School of Natural Resources. Handbook 83-2. 30 p.

Greenbank, D.O. 1963. Staminate flowers

and the spruce budworm. pp 202-218 in R. F. Morris, ed. The dynamics of epidemic spruce budworm populations. Memoirs of the Entomological Society of Canada 31

Hix, D.M.; Barnes, B.V.; Lynch, A.M.;

Witter, J.A. 1987. Relationships between spruce budworm damage and site factors in spruce-fir dominated ecosystems of western Upper Michigan. Forest Ecology and Management 21: 129-140

Hudak, J.,; Raske, A.G. editors. 1982.

Review of the spruce budworm outbreak in Newfoundland - its control and forest management implications. St. John's, Newfoundland. Canadian Forestry Service, Newfoundland Forest Research Centre. Information Report. N-X-205. 280 p.

MacLean, D.A. 1980. Vulnerability of fir -

spruce stands during uncontrolled spruce budworm outbreaks: a review and

discussion. The Forestry Chronicle 56: 213-221

MacLean DA. 1982. Forest management. pp 138-140 in J. Hudak and A.G. Raske, (editors), Review of the spruce budworm outbreak in Newfoundland- its control and forest management implications. St. John's, Newfoundland. Canadian Forestry Service. Information Report N-X-205. 280 p.

MacLean, D.A. 1996. Forest management

strategies to reduce spruce budworm damage in the Fundy model forest. Forestry Chronicle 72: 399-405

MacLean, D.A.; MacKinnon, W.E. 1997.

Effects of stand and site characteristics on susceptibility and vulnerability of balsam fir and spruce to spruce budworm in New Brunswick. Canadian Journal of Forest Research 27: 1859-1871

MacLean, D.A.; Ostaff, D.P. 1989. Patterns

of balsam fir mortality caused by an uncontrolled spruce budworm outbreak. Canadian Journal of Forest Research 19: 1087-1095

MacLean, D.A.; Piene, H. 1995. Spatial and

temporal patterns of balsam fir mortality in spaced and unspaced stands caused by spruce budworm defoliation. Canadian Journal of Forest Research 25: 902-911

Miller, A.,; Rusnock, P. 1993. The rise and

fall of the silvicultural hypothesis in spruce budworm (Choristoneura fumiferana) management in eastern Canada. Forest Ecology and Management 61: 171-189

Mott,D.G.1980. Spruce budworm: protection

management in Maine. Maine Forestry Review 13: 26-33

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Needham, T.; Kershaw, J.A.; MacLean, D.A.; Su, Q. 1999. Effects of mixed stand management to reduce impacts of spruce budworm defoliation on balsam fir stand-level growth and yield. Northern Journal of Applied Forestry 16: 19-24

O.M.N.R. 1997. Silvicultural guide to

managing for black spruce, jack pine and aspen on boreal forest ecosites in Ontario. Version 1.1. Ontario Ministry of Natural Resources, Toronto, Ontario. Book II. 370 pp.

O.M.N.R. 1998. A silvicultural guide for

the Great Lakes- St. Lawrence conifer forest in Ontario. Ontario Ministry of Natural Resources. Toronto, Ontario. 424p.

Osawa, A.1989. Causality in mortality

patterns of spruce trees during a spruce budworm outbreak. Canadian Journal of Forest Research 19: 632-638

Osawa, A.; Spies, C.J. III; Dimond, J.B.

1986. Patterns of tree mortality during an uncontrolled spruce budworm outbreak in Baxter State Park, 1983. Maine Agricultural Experiment Station. Technical Bulletin 121.

Piene, H.,and MacLean, D.A. 1999. Spruce

budworm defoliation and growth loss in young balsam fir: patterns of shoot, needle and foliage weight production over a nine-year outbreak cycle. Forest Ecology and Management 123: 115-133

Piene, H.; Ostaff, D.P.; Eveleigh, E.S. 2001.

Growth loss and recovery following defoliation by the balsam fir sawfly in young, spaced balsam fir stands. The Canadian Entomologist 133: 675-686

Royama, T. 1992. Analytical population dynamics. 1st ed. Population and Community Biology Series. 10. London, New York: Chapman & Hall

Rose AH, Lindquist OH, revised by Syme P.

1994. Insects of eastern spruces, fir and hemlock. Ottawa, ON, Natural Resources Canada, Canadian Forest Service, 159 p.

Schmitt DM, Grimble DG, Searcy JL,

technical coordinators. 1984. Managing the spruce budworm in eastern North America. Washington, D.C. US Department of Agriculture. Spruce Budworms Handbook 620. 177 p.

Steinman, J.R., and MacLean, D.A. 1994.

Predicting effects of defoliation on spruce-fir stand development: a management-oriented growth and yield model. Forest Ecology and Management 69: 283-298

Su, Q.; MacLean, D.A.; Needham, T.D.

1996. The influence of hardwood content on balsam fir defoliation by spruce budworm. Canadian Journal of Forest Research 26: 1620-1628

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Insect: Jack pine budworm, Choristoneura pinus pinus Freeman Distribution: Jack pine budworm is found throughout the areas where jack pine grows, from Alberta to New Brunswick and in the Great Lakes States. It is particularly common in the Great Lakes States, Manitoba and Ontario. Host: Jack pine is the preferred host. Eastern white, red and Scots pine are sometimes attacked but usually only when they are growing adjacent to or in the same stand as jack pine. Host damage: The larvae of jack pine budworm are defoliators. In the spring, young larvae begin feeding on pollen cones, moving to the current year�s needles as the latter develop. They consume the basal portion of the needles, webbing shoots together to form feeding shelters. The larvae feed on one and two year-old needles after the supply of the current year�s needles diminishes. Desiccation of clipped and webbed foliage causes it to turn brown. Because feeding takes place first in the tops of trees, top kill and deformities (crooks and multiple leaders) are common. Jack pine budworm is considered by many to be the most important insect pest of jack pine, causing substantial tree mortality in

some areas, particularly where trees are

drought stressed (Ives and Wong 1988; Hopkin and Howse 1995; McCullough 2000). Outbreaks in Ontario generally persist for 2 to 4 years occurring roughly every decade (Hopkin and Howse 1995). An excellent review of the ecology and factors that affect the population dynamics can be found in McCullough (2000). Hopkin and Howse (1995) and Gross et al. (1996) reviewed the many studies on the impact of jack pine budworm in Ontario. Severe defoliation rarely occurs for more than one year in a stand (McCullough et al. 1996). The impact of only one-year of moderate defoliation is not great. Defoliation for more than one year at moderate to severe levels will cause a significant growth loss and mortality. Cumulative growth losses range from 40 to 240% and are evident 3-6 years after the onset of defoliation. Trees with 50% or more defoliation are more likely to have dead tops and recover more slowly to pre-infestation growth rates. An average of 15-20% of trees can be top-killed during a single outbreak (Conway et al.1999; Hopkin and Howse 1995). Whole tree mortality ranges from 13 to 60% and is most evident among the intermediate to suppressed trees. On average, about 15% of the trees died following recent outbreaks in Canada and the United States (Conway et al.1999, Hopkin and Howse 1995). A high degree of variability in defoliation, growth loss and mortality within and among stands is frequently encountered. When dead and top-killed trees build up in the forest and wildfires occur, conditions for subsequent jack pine regeneration are provided (McCullough 2000). Habitat. Jack pine budworm is typically a pest of mature trees. Poorly stocked or overstocked stands, stands that are over-mature, and stands with low vigour trees are the most susceptible to attack and vulnerable to damage. All of these types of stand

Jack pine budworm damage

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conditions typically have trees with abundant pollen cones, which are very critical to the survival of young budworm larvae (Nealis and Lomic 1994; Nealis 1995). Mallett and Volney (1990) found no clear indication that infection by root pathogens (e.g., Armillaria) determines the extent to which trees are damaged by the jack pine budworm or whether repeated defoliation by the budworm predisposes trees to root pathogen attack. Gross et al. (1996), note that where Armillaria was present in jack pine (not common), it was associated with an increase in mortality and overall growth loss in jack pine budworm defoliated stands. Forest Management Guidelines and Recommendations Many of the important caveats outlined for spruce budworm apply for the jack pine budworm. Again, long term, quantitative studies on how forest structure and forest management affect populations of jack pine budworm are lacking. And again, until these studies are done, we can only proceed on the basis of what appears to make sense based on the knowledge of insect ecology and a retrospective analysis of past outbreaks. The overall strategy to dampen the impact of jack pine budworm outbreaks is to develop jack pine stands that are less susceptible to being attacked and less vulnerable to significant mortality and topkill. The two key components of a forest management strategy for jack pine budworm are to reduce the amount of pollen cones (staminate or male flowers) in an area, and to promote tree vigour so that the trees are less vulnerable to damage and death. Many of the approaches to do this have been described by Hodson and Zehngraff (1946), Jones and Campbell (1986), McCullough et al. (1994), Albers et al. (1995), and Weber (1986, 1995). Recent studies by McCullough et al. (1996), Kouki

et al. (1997), Conway et al. (1999) and Radeloff et al. (2000) have refined general forest management approaches. The recommendations outlined below have been drawn largely from these sources. Pre-outbreak stands: To reduce the susceptibility of attack and vulnerability to damage, before outbreaks occur, consider the following. Manage to a predetermined rotation age to avoid overmature stands. Stand age is the most important factor to be considered in the management of jack pine budworm, because operationally forest managers have more control over rotation ages than site quality or stand density (Conway et al. 1999). Overmature stands have trees of low vigour and ones that are less tolerant of budworm damage. Moreover, older stands damaged by budworm are more likely to become attacked by secondary pests such as the pine engraver beetle, Ips pini (Say), Armillaria root disease, and blowdown. McCullough et al. (1996) observed that once stands in northern Michigan reached about 50-55 years, vulnerability to budworm-related mortality increased rapidly with stand age. A rough rule of thumb would be to determine first when a stand typically begins to stagnate and deteriorate in the area and then to set the harvest date about 5 years before this happens. Shortening the rotation age reduces the vulnerability of the forest to budworm damage. Annual harvests should be allocated to those stands at greatest risk. Albers et al. (1995), Jones and Campbell (1986), McCullough et al. (1994), and Weber (1986, 1995) have consistently supported this recommendation. Maintain proper stocking. Optimal stocking will encourage stand vigour and reduce the number of staminate flowers in a stand.

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Overstocked stands contain many suppressed trees, which can contain numerous pollen

cones. Also, trees with short, narrow crowns that have little needle biomass are typically found in overstocked stands and can be quickly defoliated and killed in budworm outbreaks. In under-stocked stands, top kill is usually greater especially in mature to overmature stands. For the Lake States region, Albers et al. (1995) and Weber (1986, 1995) suggest that stocking should be maintained between 16 to 25-35 m2/ha of basal area. The conventional wisdom is to remove �wolf trees� from stands because they have full and large crowns typically with abundant pollen cones. These trees are thought to act as budworm reservoirs during outbreaks increasing the overall vulnerability of the stand. McCullough et al. (1996) however found no strong evidence that wolf trees increased stand vulnerability to tree mortality. Priority should be given to maintaining optimal stocking levels. The removal of wolf trees may be considered optional if there is a market for the trees. Thinning good quality stands to remove suppressed, intermediate and wolf trees has been suggested to reduce the impact of the budworm. Recent studies by Conway et al. (1999) however have shown that the presence of suppressed trees does not appear

to adversely affect the volume or value in a stand. These authors suggest that pre-commercial thinning from below should be given low priority as a forest management technique to reduce the impact of jack pine budworm. Studies designed to compare the susceptibility and vulnerability of thinned stands (either pre-commercial or commercial) and unthinned stands are lacking. Researchers have speculated that thinned stands would produce more pollen cones and thus make them more vulnerable to damage. This hypothesis needs to be tested. Ultimately the forest manager must weigh the balance between producing greater wood volume through thinning and the possible risk of increased damage by the budworm. Avoid creating uneven-aged or two-storied stands. In situations where stands have a well-stocked understory but a second older under-stocked overstory, attempt to remove the overstory trees as soon as possible. During a budworm outbreak, these overstory trees, which typically have abundant pollen cones, can support large populations of budworm. These budworms can spin down or get blown down to the smaller trees and soon defoliate and kill them. Regenerate jack pine by clearcutting. Standing dead trees, hardwoods or less susceptible species such as eastern white pine can be left to promote diversity. Site quality. Low quality sites were once thought intuitively to be inappropriate for jack pine stands. McCullough et al. (1996) and Kouki et al. (1997) observed, contrary to expectations, that mortality was lower on poor sites with low site index values than on better sites with higher site index values. Defoliation and site index were not correlated and thus differences in defoliation alone did not explain why mortality was highest on relatively good sites (Kouki et

Healthy jack pine stand

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al.1997). Conway et al. (1999) suggest that trees growing on low quality sites may have increased tolerance to stress, or conversely that trees growing on higher quality sites have higher foliar nitrogen levels, which are positively associated with larval survival. Encourage age class diversity across the landscape. Whenever possible, promote age class diversity in large jack pine areas to reduce the overall susceptibility and vulnerability to jack pine budworm at any one time and in any one area. Large, contiguous areas of mature and overmature jack pine should be avoided. Where there are large natural stands or plantations of jack pine of the same age that are close to rotation age, stagger three clear-cuts over a 10-year period to break-up (diversify) the area. Weber (1986, 1995) advised that when block- or patch-cutting jack pine stands, attempt to minimize the amount of edge created. Jack pine trees left at the edge tend to respond with profuse crops of pollen cones. The best shapes of harvest areas are large squares, broad rectangles, or broad ovals. Avoid thin strip cuts; aesthetic leave strips or islands, especially during a budworm outbreak. Avoid leaving trees along a roadside during an outbreak because they typically succumb to death within a few years and must be harvested later to �improve aesthetics� or reduce hazards. Kouki et al. (1997) and Radeloff et al. (2000) examined the significance of stand edges. Kouki et al. (1997) observed that young stands adjacent to older stands (5 years older or more) increased the level of defoliation in the older stands. They speculated that the young stands had increased amounts of pollen cones because of a greater exposure to light. This finding therefore appears to contradict the recommendation to encourage the break up of age classes across the

landscape. The authors do caution that additional studies are needed to verify these results before general recommendations can be made. Radeloff et al. (2000) found that edge had both a negative and positive effect and that this change in direction was related to the different phases of the outbreak. Up to the peak of the outbreak, edge density of budworm populations was positively correlated thus possibly supporting the hypothesis that pollen cones along the edge provided better food habitat for the budworm. After the outbreak peak, edge density was negatively correlated; that is, the edge helped decrease the populations of budworm. It is known that predators respond with a time lag to more abundant prey, and that higher numbers of predators occur along stand edges. Radeloff et al. (2000) concluded that edge was not significantly related to budworm populations and that the positive and negative effects seem to counteract each other over the course of the outbreak. So where does this leave us, in terms of management recommendations for edges and age structure? On balance, and in the absence of additional research, it seems prudent at this time to attempt to minimize edges to reduce the production of pollen cones. The relationship between pollen cones and the survival of young jack pine budworm is clear and unequivocal. It therefore makes sense that if we wish to reduce the susceptibility of jack pine stands to the budworm at the beginning of an outbreak that we reduce the amount of pollen and the edge, which encourage pollen cone production through increased light. Increasing the age-class diversity across the landscape also makes sense in that the evidence strongly suggests that as the age of the stand increases so does the susceptibility to attack and vulnerability to damage. Therefore reducing the amount of

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forest that is susceptible at any one time may reduce the overall impact and volume of wood that needs to be salvaged. Increasing age and species diversity (see below) across the landscape also has broader ecological benefits to species diversity. Promote species diversity across the landscape. Wherever possible, establish less susceptible species to reduce the overall impact of the jack pine budworm on the forested landscape. Red pine is not a favoured host of the budworm and often can be established on many sandy jack pine sites. On better quality sites, consider establishing white pine or trembling aspen. As a rule of thumb, aim to maintain about half of the area in non-host or less susceptible tree species. Post-outbreak stands: When severe defoliation has occurred or is expected to occur, pre-salvage and salvage of affected stands will reduce the impact and preserve most of the value of the wood. Harvest high-hazard stands and areas of heavy defoliation first. Overstocked stands should be given high priority for salvage (Conway et al. 1999). References Albers J.; Carroll, M.; Jones, A. 1995. Jack

pine budworm in Minnesota: past trends and changing perspectives. pp. 11-18 in Jack Pine Budworm Biology and Management. Proceedings of the Jack Pine Budworm Symposium, Winnipeg, Manitoba, January 24-26, 1995. Edmonton, Alberta. Natural Resources Canada, Canadian Forest Service, Northwest Region. Information Report. NOR-X-342. 158 p.

Conway, B.E.; McCullough, D.G.; Leefers, L.A. 1999. Long-term effects of jack pine budworm outbreaks on the growth of jack

pine trees in Michigan. Canadian Journal of Forest Research 29: 1510-1517

Gross, H.L.; Hopkin, A.A.; Howse, G.M.

1996. Impact of the jack pine budworm in Ontario. Sault Ste. Marie, ON. Canadian Forest Service, Natural Resources Canada. Frontline. Technical Note No. 87. 4 p. p.

Hodson, A.C.; Zehngraf, P.J. 1946.

Budworm control in jack pine by forest management. Journal of Forestry 44: 198-200

Hopkin, A.A.; Howse, G.M. 1995. Impact of

the jack pine budworm in Ontario: a review. pp. 111-119 in Jack Pine Budworm Biology and Management. Proceedings of the Jack Pine Budworm Symposium, Winnipeg, Manitoba, January 24-26, 1995. Edmonton, Alberta. Natural Resources Canada, Canadian Forest Service, Northwest Region. Information Report NOR-X-342. 158 p.

Ives, W.G.H.; Wong, H.R. 1988. Tree and

shrub insects of the prairie provinces. Edmonton, Alberta. Canadian Forestry Service, Northern Forestry Centre. Information Report. NOR-X-292.

Jones, A.C.; Campbell, J. 1986.Jack pine

budworm: the Minnesota situation. pp. 7-9 in Jack Pine Budworm Information Exchange. Winnipeg, Manitoba. Manitoba Department of Natural Resources. 96 p.

Kouki, J.; McCullough, D.G.; Marshall, L.D.

1997. Effect of forest stand and edge characteristics on the vulnerability of jack pine stands to jack pine budworm (Choristoneura pinus pinus) damage. Canadian Journal of Forest Research 27: 1765-1772

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Mallett,K.I.,; Volney,W.J.A. 1990.

Relationships among jack pine budworm damage, selected tree characteristics, and Armillaria root rot in jack pine. Canadian Journal of Forest Research 20: 1791-1795

McCullough, D.G. 2000. A review of factors

affecting the population dynamics of jack pine budworm (Choristoneura pinus pinus Freeman). Population Ecology 42: 243-256

McCullough, D.G.; Katovich, S.; Heyd,

R.L.; Weber, S. 1994. How to manage jack pine to reduce damage from jack pine budworm. U. S. Department of Agriculture, Forest Service, Northeastern Area, State and Private Forestry. NA-FR-01-94:7pp. www.na.fs.fed.us/spfo/pubs/howtos/ht_jack/ht_jack.htm(accessed on 9 April 2002)]

McCullough, D.G.; Marshall, L.D.; Buss,

L.J.; Kouki, J. 1996. Relating jack pine budworm damage to stand inventory variables in northern Michigan. Canadian Journal of Forest Research 26: 2180-2190

Nealis, V.G. 1995. Population biology of the

jack pine budworm. pp. 55-71 in Jack Pine Budworm Biology and Management. Proceedings of the Jack Pine Budworm Symposium, Winnipeg, Manitoba, January 24-26, 1995. Edmonton, Alberta. Natural Resources Canada, Canadian Forest Service, Northwest Region. Information Report. NOR-X-342. 158 p.

Nealis, V.G.; Lomic, P.V. 1994. Host-plant

influence on the population ecology of the jack pine budworm, Choristoneura

pinus (Lepidoptera: Tortricidae). Ecological Entomology 19: 367-373

Radeloff, V.C.; Mladenoff, D.J.; Boyce, M.S.

2000. The changing relation of landscape patterns and jack pine budworm populations during an outbreak. Oikos 90: 417-430

Weber, S.D. 1986. Jack pine management.

pp. 12-14 in Jack Pine Budworm Information Exchange. Winnipeg, Manitoba. Manitoba Department of Natural Resources. 96 p.

Weber, S.D. 1995. Integrating budworm into

jack pine silviculture in northwest Wisconsin. pp. 19-24 in Jack Pine Budworm Biology and Management. Proceedings of the Jack Pine Budworm Symposium, Winnipeg, Manitoba, January 24-26, 1995. Edmonton, Alberta. Natural Resources Canada, Canadian Forest Service, Northwest Region. Information Report NOR-X-342. 158 p.

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Insect: White pine weevil, Pissodes strobi (Peck) Distribution: The white pine weevil is found throughout Canada and the northern United States. Hosts: Eastern white pine is the most common and preferred host in eastern Canada. Other hosts include jack, lodgepole, pitch, Scotch and occasionally red pine; and, black, blue, red, white, Sitka, Engelmann and Norway spruce (Wallace and Sullivan 1985). Host Damage: In the spring, adults feed on the previous years' terminal shoot and lay eggs in the feeding punctures. The larvae feed on the phloem and progress downward on the leader eventually forming a �feeding ring� and girdling the stem. The terminal

withers, reddens and eventually dies, forming a �shepherd�s crook.” Weevils often kill two years of growth and sometimes as much as three to four years of growth in a single year. Leader damage results in loss of height growth and deformed main stems. Typically, one of the lateral branches assumes dominance, with a resulting crook where the lateral joins the main stem. Occasionally, two laterals may compete equally for some time and a fork is formed. Acute branch angles (often encased in bark) are common. Repeated attacks may result in suppressed

trees, which are prone to being killed by competing vegetation. The overall impact of the weevil depends on: how many trees are affected in the stand; the number of weevil injuries per tree; how well the tree recovers stem form and maintains height growth; and, ultimately on the target products (e.g., pulpwood, sawlogs, veneer). Over time, and as the tree increases its radial growth, damage to the terminal becomes less apparent. Many mature trees have internal evidence of weevil attack but do not have an obvious stem crook. Loss estimates vary widely and reflect in part the local conditions of the stand (open-grown trees are much more heavily attacked than those grown in partial shade), geographic location, sawmilling standards, tree size and rotation age. For eastern white pine, achieving a defect-free 5 m first log is a common goal. There is a considerable body of literature on the impact of the weevil on eastern white pine in eastern North America and on Sitka and interior spruce in western North America, but virtually none on the remaining host species. Habitat: The weevil is most prevalent on young open-grown stands. Once crown closure is achieved, it is seldom a problem. Weevils attacking eastern white pine generally prefer fast growing tree with leaders that are greater than 4.0 mm in diameter and have bark thicker than 0.8 mm (Sullivan 1961; Wallace and Sullivan 1985). Weevils also prefer long, upright terminal stems (Vandersar and Borden 1977). Open-grown trees suffer considerable damage. Increasing the amount of overhead shade reduces injury from the weevil (e.g., (Peck 1817; Graham 1918, 1926; Peirson 1922). Sullivan (1961) noted that when isolation is reduced by just 25-50%, weevil damage is reduced by about 10%.

White Pine weevil damage

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Shady conditions reduce ambient temperature and heat accumulation in the stand. Studies by Sullivan (1961) demonstrated that weevils in shaded stands feed and oviposit in an irregular pattern on as many as 4 to 5 years' growth (normally one years' growth in open stands). Under shaded conditions, females fail to deposit a sufficient number of eggs in a localized area of the main stem to provide enough larvae to form a feeding ring. Without this feeding ring, isolated larvae or small groups of larvae are insufficient in number to overcome the resin flow in the leader and are eventually drowned or trapped in the resin. Furthermore, the leaders in shaded areas are often too small (they are less than 4 mm wide and have less than 0.8 mm of bark) to be attractive for oviposition and do not provide sufficient food for weevil larvae. The lower temperature of shaded leaders also retards larval development resulting in longer exposure to natural enemies (Wallace and Sullivan 1985). Weevils that hibernate within shaded areas have higher mortality during the winter (Wallace and Sullivan 1985). Forest Management Guidelines and Recommendations Silvicultural practices to reduce the impact of the weevil are aimed at providing shaded conditions that make the habitat unsuitable for the weevil (Sullivan 1961; Wallace and Sullivan 1985). Shade can be provided by: i) growing the trees underneath a canopy (overhead shade); ii) growing trees adjacent to taller trees (side shade); or, iii) establishing crown closure quickly. Provide overhead shade Overhead shade can be provided by using a uniform shelterwood, underplanting, or by using a nurse crop. Each particular system

for regeneration has it merits reflecting the silvics of the species, the current site and stand conditions, available resources, and the need to consider wildlife, genetic, cultural and economic values. Uniform shelterwood. As the name implies, shelterwood provides a shelter or habitat that is favourable to the growth and development of the tree. In Ontario, eastern white pine is managed predominately under the uniform shelterwood system and less frequently under the clearcut system (Pinto 1992). White spruce can also be managed under uniform shelterwood. Growing trees in shade requires a trade-off between survival and overall growth (Katovich and Morse 1992). Overstory trees may also create a physical barrier to the leaders of the understory eastern white pine and subsequently damage them. The balancing act that foresters must do when growing eastern white pine in an understory is to provide enough sunlight to allow adequate growth of the leaders, yet enough shade to create unfavourable conditions for the weevil. In a shelterwood system, the existing stand provides both a seed source and shade for regeneration (Stiell 1985). In a uniform shelterwood system for eastern white pine, an initial preparatory cut is done to open the mature stand, and promote crown expansion, seed production and stem volume. A regeneration or seeding cut is done next to favour germination and provide space for seedlings and finally a removal cut takes the remaining trees after the regeneration is well-established (Stiell 1985). In the preparatory cut, trees are ideally spaced at 25-30% of their height; in the seeding cut the residual trees are spaced at about 40% of their height (Pinto 1992). A target of 50% canopy cover after the seeding should be aimed for.

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Methods to estimate this are provided by Bentley (1996). To ensure high quality first logs, the removal cut should wait until the eastern white pine regeneration is at least 5 m tall. These 3-cut shelterwood cuts appear to work well in Ontario in providing good regeneration and weevil control (Szuba and Pinto 1991). The removal cut may also be done twice (4-cut shelterwood), once when the white pine regeneration is less than 6 m and again when the regeneration is beyond 6 m (Pinto 1992). Underplanting. Underplanting of eastern white pine under hardwood canopies has been successful in some areas in Ontario (Szuba and Pinto 1991). However, underplanting under a conifer or mixed conifer stand is likely to provide more shade early in the spring when weevils first become active than would intolerant hardwoods which begin leaf flush around the same time. When using this technique to reduce the impact of the white pine weevil, the key is to provide enough sunlight for adequate growth of the tree and yet enough shade to create unfavourable conditions for the weevil. This tradeoff is the same as the shelterwood system. Because eastern white pine seedlings can obtain maximum height growth in as little as 45% of full sunlight (Logan 1966; Stiell 1985; Messier et al. 1999), one should probably aim for a maximum of 40-50% full sunlight in the understory. A rule of thumb for 8-15 year-old eastern white pine is that they should grow about 40 cm per year. If they are growing less, they probably require more light (Katovich and Mielke 1993). The same advice would apply if a shelterwood system was being used. Under-planted eastern white pine should be protected until trees reach at least 5 m in height. An alternative to underplanting under the entire canopy is removal of the overstory in 3-m wide strips, planting therein, and leaving 5-m

bands between the cut-strips (Messier et al. 1999). Periodic release will be required and competition may be needed to ensure adequate survival of the under-planted trees. Katovich and Morse (1992) examined the growth response of young understory white pine (about 2 m tall), and incidence of weevil to four levels of canopy removal (about 0, 7, 11, and 16 m2 of basal area (BA) per ha). They found that maintaining about 7-11 m2 BA appeared to be a good compromise between increasing growth and mitigating weevil damage. In other words, removing too much of the overstory resulted in increased damage by the weevil, but not removing enough resulted in reduced leader growth. Messier et al. (1999) suggest two approaches for releasing white pine planted underneath a hardwood story: i) a low intensity thinning that allows at least 10% of photosynthetic photon flux density (PPFD, i.e., above-canopy light) followed by a more intensive thinning, or ii) a higher intensity thinning initially (30-40% PPFD, followed a few years later by understory brushing. Nurse crops. An alternative to a high-density single species plantation (see below) is the establishment of a mixed species stand where one species grows faster than the other and serves as a �nurse crop�. Nurse crops are established at the same time as the other tree species. Nurse crops could be hardwood species or other conifer species that are less susceptible to the weevil. Hardwood nurse crops could work well for eastern white pine and white spruce, which can tolerate some shade. (Struik 1978) recommends that white pine always be established with a nurse crop. Szuba and Pinto (1991) cautioned that it is important to carefully evaluate the site when planning to grow eastern white pine with a nurse crop such as aspen. For example, aspen grown on poor quality sites (e.g., dry, rapidly

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drained sites) may not grow fast enough to provide sufficient shade and protect eastern white pine from the weevil. It is very important to ensure that the nurse crop grows at least as fast as the desired species in order to provide shade during the period of the first 20 years or so. Planting white pine with another conifer (usually in alternate rows) has been advocated for some time (e.g. (Peirson 1922) but has produced mixed results (Peirson 1922; MacAloney 1943 (revised); Belyea and Sullivan 1956). The main objective is to have the less susceptible alternate species out-top the highly susceptible white pine thus providing shade and the associated unfavourable condition for the weevil. To be effective, field observations suggest that the alternate conifers should be at least 60 cm above the canopy when white pine are 2 m or less and at least 1 m when white pine are more than 2 m (Peirson 1922). In most cases the alternate species may need to be planted before white pine to gain the height advantage, in which case it would be considered underplanting rather than a nurse crop. Struik (1978) suggests a maximum of 50% of sunlight is the most practical compromise for seedling growth and weevil management when using nurse crops for eastern white pine. Stand density and light intensity must be carefully regulated for the first 20 years of the plantation, which is best achieved through release treatments (gradual or every 5 years) that selectively remove individual stems. The timing of the release treatment is very critical and should be done when the leader shows a gradual reduction in growth (as a result of suppression) but is still vigourous enough to respond to release (Struik 1978). Tending white pine on fertile soils may be futile, because costs will be high [to manage the competing vegetation].

Working with white spruce in the interior of British Columbia, (Taylor et al. 1996) demonstrated that the number of trees attacked by the weevil diminished as the percent of overtopping crown cover increased. They noted that measuring crown cover (in 19% classes) gave as good or better relationship between current weevil attack and leader length as the more complex light-interception measurements. Removal of the overstory should first be done in areas where the weevil infestation is light followed by areas where the infestation is heavier. Provide side shade Another variant of the shelterwood system is the strip shelterwood where narrow parallel clearcuts are seeded by the residual stand, which also provides side shade (Stiell 1985). (Stiell and Berry 1985) examined the incidence of weevils in clearcut strips that would admit nominal values of 25, 50, 75 and 100% of full sunlight. The incidence of weevil attack diminished with decreasing amounts of sunlight. Stiell and Berry (1985) concluded that strips cut in a north-south direction, and with a strip width to stand ratio of 0.66 to 1.0 (50-75% of full light), resulted in an adequate number of white pine trees to reach 5 m free from weevil damage. The regeneration established in strips would require release to reduce mortality from suppression. Strip shelterwood was not effective in hardwood stands because the hardwoods were leafless early in the spring when the weevils were active. Better results might have been obtained if the strips had been aligned to minimize exposure to direct sunlight (Stiell and Berry 1985). (Taylor and Cozens 1994) found that alternating strips of overstory shade (5 m wide) and no shade (7m wide) oriented in an east-west direction, reduced weevil attacks by 2-6% on interior white spruce. Attack rates were low (< 2%) when the treatments were started and had the

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attack rates been higher (e.g., 15-20%), larger differences among the treatments may have been possible (Taylor and Cozens 1994). Taylor and Cozens (1994) observed that it took at least three full growing seasons before overhead or side shade treatments had a noticeable reduction of weevil damage. Grow trees quickly to crown closure Shade intolerant species like jack pine and black spruce are managed under the clearcut system and are typically established as single species stands from seed (natural or artificial) or seedlings (OMNR 1997, 1998). Plantations of eastern white pine may be used on these clearcut sites to restore areas where it is formerly was present, where stand conversion is planned, or to afforest old fields (OMNR 1998). White pine may also be used where competition with advanced reproduction, such as on shallow tills of the Canadian Shield, would be very severe. Planting eastern white pine in dense plantations has been advocated and investigated for some time (e.g., Peirson 1922; Graham 1926). The main objective for weevil management is to grow the trees as quickly as possible to crown closure to create shaded conditions, which are unsuited to the weevil. This technique is not failsafe because weevils will attack trees before shading reaches a level that is unsuitable for the weevil. Weevil populations typically take several years to develop to high levels, thus the sooner the plantation reaches crown closure the lower the levels of weevil damage. Maintaining high levels of stocking and tree vigour are essential for this technique to have success (MacAloney 1943). Trees in high density plantations (less than 2 m by 2 m spacing) tend to have better form of the main stem because the close spacing

forces the weevilled trees to grow in height (�correcting themselves�) rather than laterally. The trade off with rapid height growth is that diameter growth of the leader is reduced. Graham (1926) suggests that if a density of 2960 (about 1.8 by 1. 8 m spacing) to 3700 trees per hectare (about 1.6 by 1.6 m spacing) is maintained through the first 20-25 years of the plantation, losses from the weevil will be minimal. (Alfaro and Omule 1990) found Sitka spruce (Picea sitchensis) spaced at 2.7 by 2.7 m had less weevil damage than trees spaced 3.6 or 4.6 m apart. Close spacing reduces, but does not eliminate damage from the weevil (Graham 1926; Alfaro and Omule 1990). High-density plantations of eastern white pine should not be established in high-hazard white pine blister rust zones. A high density of trees becomes a liability in plantations if they are not tended. Untended stands have very slow diameter growth and high natural mortality, especially in the lower crown classes. Stiell (1979) observed that untended stands of eastern white pine do not produce a sufficient number of unweevilled trees at harvest. The fate of untended spruce or jack pine plantations that were weevilled is unknown, but it is very likely that these species will have fewer weevilled trees because they are less preferred than eastern white pine. The threshold for economic loss for spruce and jack pine in eastern Canada is unknown. Pre-commercial thinning is required in high-density stands to promote survival and growth of trees. The earliest thinning for eastern white pine should be scheduled when the crop trees reach 5 m in height (1 log length), leaving about 370 undamaged stems per hectare (Steill 1979, 1985). First release thinning could be delayed until there are only about 370 crop trees per hectare, which would allow commercial thinning and

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diminish risk of sun scorch. The drawbacks the delayed thinning include slow growth response of the remaining trees because of short crowns and possibly an unsatisfactory distribution of undamaged trees within the stand (Steill 1979). Alfaro and Omule (1990) recommended close spacing of Sitka spruce with precommercial thinning at age 25 to allow a first log of good quality. Similarly, Maclauchlan and Borden (1996) recommended delaying pre-commercial thinning of lodgepole pine attacked by the closely related terminal weevil (P. terminalis) until the trees are at least 15 years old or until the base of the crown has lifted above the top of the first log. Although no specific prescriptions for thinning weevilled stands of white or black spruce and jack pine have been developed, the guiding principle of waiting to do a precommercial thinning until one log length has been produced appears reasonable. Even in the weevil-preferred eastern white pine stands, some trees will escape attack and become suitable crop trees. Retaining weevil-free and usually smaller trees in eastern white pine plantations while removing the more vigourous, heavily weevilled trees does not result in selection against rapid growth (Ledig and Smith 1981). In Ontario, high density eastern white pine plantations show low levels of weevil damage and probably work the best on good sites where trees are vigourous enough to grow well (Szuba and Pinto 1991). In a survey of 30 to 80 year-old eastern white pine growing in well-stocked and unsuppressed plantations in Wisconsin, Pubanz et al. (1999) found at least one weevil injury in 87% of the crop trees examined. The average volume deduction due to crook in the first log (5 m) was only 1.3%. If eastern white pine is to be established in plantations, Pubanz et al. (1999) make five

important recommendations: 1) maintain good stocking; 2) promote vigour (good crown development and diameter growth); 3) thorough selective thinning of unthrifty and heavily weevilled trees; 4) prune trees to improve the lumber grade recovery of crop trees or to move non crop trees to crop tree status; and, 5) focus on the number of crop trees in a stand rather than how many non crop trees are present. References Alfaro, R.I.; Omule, S.A.Y. 1990. The effect

of spacing on Sitka spruce weevil damage to Sitka spruce. Canadian Journal of Forest Research 20: 179-184

Belyea, R.M.; Sullivan, C.R. 1956. The

white pine weevil (Pissodes strobi): A review of current knowledge. The Forestry Chronicle 32: 58-67

Bentley, C.V. 1996. Prediction of residual

canopy cover for white pine in central Ontario. Sault Ste. Marie, ON. Natural Resources Canada, Canadian Forest Service, NODA note No. 20, 5 pp.

Graham, S.A. 1918. The white-pine weevil

and its relation to second-growth white pine. Journal of Forestry 16: 192-202

Graham, S.A. 1926. The biology and control

of the white pine weevil, Pissodes strobi Peck. Ithaca, N. Y. Cornell University Agricultural Experiment Station, Bulletin 449, 32 pp.

Katovich, S.; Mielke, M.E. 1993. How to

manage eastern white pine to minimize damage from blister rust and white pine weevil. USDA, Forest Service, State and Private Forestry, NA-FR-01-93. 8 pp.

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Katovich, S.A.; Morse, F.S. 1992. White pine weevil response to oak overstory girdling - results from a 16-year-old study. Northern Journal of Applied Forestry 9: 51-54

Ledig, F.T.; Smith, D.M. 1981. The

influence of silvicultural practices on genetic improvement: height growth and weevil resistance in eastern white pine. Silvae Genetica 30: 30-36

Logan, K.T. 1966. Growth of tree seedlings

as affected by light intensity. II. Red pine, white pine, jack pine, and eastern larch. Ottawa, ON. Department of Forestry, Publication 1160

MacAloney, H.J. 1943. The white-pine

weevil (revised). Washington, D.C. United States Department of Agriculture, Circular 221, 31 pp.

Maclauchlan, L.E.; Borden, J.H. 1996.

Spatial dynamics and impacts of Pissodes terminalis (Coleoptera:Curculionidae) in regenerating stands of lodgepole pine. Forest Ecology and Management 82: 103-113

Messie,C.;Parent,S.;Chengaou,M. ; Beaulieu,

J. 1999. Juvenile growth and crown morphological plasticity of eastern white pines (Pinus strobus L.) planted along a natural light gradient: results after six years. The Forestry Chronicle 75: 275-279

O.M.N.R. 1997. Silvicultural guide to

managing for black spruce, jack pine, and aspen on boreal forest ecosites in Ontario. Book II: Ecological and management interpretations for northwest ecosites. Version 1.1. Ontario Ministry of Natural Resources, Queen�s Printer for Ontario, Toronto, 370 pp.

O.M.N.R. 1998. A silvicultural guide for the Great Lakes- St. Lawrence conifer forest in Ontario. Ontario Ministry of Natural Resources. Queen�s Printer for Ontario, Toronto. 424 pp.

Peck, W.D. 1817. On the insects which

destroy the young branches of the pear tree and the leading shoot of the Weymouth pine. Journal of Massachusetts Agriculture 4: 205-211

Peirson, H.B. 1922. Control of the white

pine weevil by forest management. Harvard University. Harvard Forest Bulletin 5, 42 pp.

Pinto, F. 1992. Silvicultural practices in

Ontario's white pine forests. pp 170-178 in The White Pine Symposium: History, Ecology, Policy and Management, Duluth, Minnesota , September 16-18, 1992. St. Paul, Minnesota: Minnesota Extension Service, University of Minnesota

Pubanz, D.M.; Williams, R.L.; Congos, D.L.;

Pecore, M. 1999. Effects of the white pine weevil in well-stocked eastern white pine stands in Wisconsin. Northern Journal of Applied Forestry 16: 185-190

Stiell,W.M. 1979. Releasing unweevilled

white pine to ensure first-log quality of final crop. The Forestry Chronicle 55: 142-143

Stiell, W.M. 1985. Silviculture of eastern

white pine. Proceedings of the Entomological Society of Ontario, 116: supplement: 95-107

Stiell,W.M.; Berry, A.B. 1985. Limiting

white pine weevil attacks by side shade. The Forestry Chronicle 61: 5-9

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Struik, H. 1978. Tending of white pine and red pine. pp 123-129 in DA Cameron (Ed). White and red pine symposium, Chalk River, ON, September 20-22, 1977. Sault Ste. Marie, ON, Great Lakes Forest Research Centre, Canadian Forestry Service, Department of the Environment, No. 0-P-6

Sullivan, C.R. 1961. The effect of weather

and the physical attributes of white pine leaders on the behavior and survival of the white pine weevil, Pissodes strobi Peck, in mixed stands. The Canadian Entomologist 93: 721-741

Szuba ,K.; Pinto, F. 1991. Natural history of

the white pine weevil and strategies to decrease its damage to conifers in Ontario. Ministry of Natural Resources, Central Ontario Forest Technology Development Unit, Technical Report 13

Taylor,S.P.;Alfaro,R.I.;DeLong,C.;Rankin,L.

1996. The effects of overstory shading on white pine weevil damage to white spruce and its effects on spruce growth rates. Canadian Journal of Forest Research 26: 306-312

Taylor, S.P.; Cozens,R.D.1994. Limiting

white pine weevil attacks by side and overstory shade in the Prince George Forest Region. Journal of the Entomological Society of British Columbia 91: 37-42

Vandersar, T.J.D.; Borden, J.H. 1977.

Visual orientation of Pissodes strobi Peck (Coleoptera: Curculiondiae) in relation to host selection behaviour. Canadian Journal of Zoology 55: 2042-2049

Wallace DR, Sullivan CR. 1985. The white

pine weevil, Pissodes strobi

(Coleoptera:Curculionidae): a review emphasizing behavior and development in relation to physical factors. Proceedings of the Entomological Society of Ontario 116: supplement: 39-62

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Insect: Pine root collar weevil, Hylobius radicis Buchanan

Distribution: The weevil is native to eastern North America and is found from Newfoundland, southward to Virginia and northwestward through the United States and Canada to Minnesota and Manitoba (Wilson and Millers 1983). Hosts: The pine root collar weevil attacks several species of native and exotic pines. Jack and red pine are more susceptible than eastern white pine. Among the various species of pines planted together or located near each other, the frequency of attack by larvae on the root collar is high on Scotch, moderate on red and jack pine and rare on eastern white pine. The order of shoot preference by adult weevils, however, is eastern white, Scotch, jack and red pine (Wilson and Millers 1983).

Host Damage: The larvae of the root collar weevil inflict the major damage to the tree, feeding on the inner bark at the base of the tree (the root collar) and roots. An area of pitch-soaked soil adjacent to the tree base indicates larval feeding. Badly damaged trees exhibit changes in the colour of their foliage, progressing from yellow to red before the needles drop off. If enough tissue is killed, the tree dies or is weakened and breaks over.

Trees repeatedly attacked each year die first. Impact varies with the host tree, its vigour and size. Scots pine is the most susceptible to attack, trees with a basal diameter from 5-10 cm die about 3 to 4 years after repeated infestation. Jack and red pine tolerate repeated infestation longer but are often windthrown as a result of stems and roots being weakened. Reduction in shoot length precedes mortality. Older trees that survive the weevil infestation may become host to secondary attacks by fungal pathogens or other insects (Wilson and Millers 1983). Mortality is greatest among plantation trees 10 cm or less in diameter (Rose et al. 1999).

Habitat: Trees growing in light sandy soils on dry sites are preferred by the pine root collar weevil. However, heavy attacks and mortality can also occur in stands near swamps and on loamy or clay soils. Infestations tend to be more severe in pine plantations and windbreaks than natural stands. Planted pines typically have a larger root collar at the soil surface and below the soil than naturally growing pines. Stands that have dense canopies following crown closure have fewer insects than poorly stocked open-grown stands. In closed stands the temperature is lower and humidity is higher, which are conditions less favourable to the weevils (Wilson and Millers 1983). Forest Management Guidelines and Recommendations

Wilson and Millers (1983) summarized the literature on the pine root collar weevil and provided guidelines to manage this weevil. The prescriptions outlined here are based on those guidelines.

Before planting, evaluate the site for weevil hazard. High-risk plantations occur where summers and winters are relatively mild, where jack, red or scots pine stands nearby are heavily infested and are dying from the Root collar weevil damage

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weevil, and where the planting is a mixture of closely related pine species or different ages of the same species. Risk drops rapidly when the infestation source is more than 1.5 km away, the climate is cooler, and where pines are planted in small monocultures or in mixtures with spruce or hardwoods. Consider planting less susceptible white pine rather than the more susceptible red and jack pine when planting in high hazard areas. Ignoring a nearby infestation source will eventually lead to serious damage and costly control treatments six to 15 years after planting.

Weevil-infested brood trees that are on or adjacent to planting site cause an infestation of the young trees 3 to 4 years after planting. Brood trees include residual trees left from logging, seed trees, windbreak trees, wolf trees, or any other tree that is infested and left on site. Choose uninfested trees as seed trees and remove infested trees whenever possible.

When establishing a new plantation, plant at a 1.8 by 1.8 m spacing to encourage early crown closure because weevil populations in these stands will drop before tree mortality occurs. Maintain stocking standards by replanting open areas caused by planting failures. The severity of damage tends to increase as planting depth increases so plant as shallowly as possible � about 10-13 cm in high hazard areas. If possible, plant trees in small solid blocks of 2.5 to 5.0 ha separated by buffers of non-host species. If large blocks are planted, then mix (e.g., alternate rows) pine with spruce or tamarack or other compatible non-host trees to reduce the risk. (Cerezke 1994)

Work to keep the trees vigourous because healthy trees are better able to resist attack by the weevil. Plant on good sites whenever possible, especially when the risk of weevil injury is high. On good sites pines tend to outgrow the weevil injury. On the other

hand, trees that are weak and dying not only encourage weevil populations to build up but they also attract secondary insects such as bark beetles, especially in dry years when the trees are under greater stress. Remove dead and dying trees from a plantation.

Survey plantations regularly during the susceptible period of tree growth (1-5 m tall) to determine the level of damage by the weevil. Monitoring plantations occasionally (once every 2 or 3 years) where the risk is high will usually reveal problems before they become too serious. If the amount of injury is unacceptable, consider pruning the lower branches (up to 1 m above the ground) and scraping the litter and about 5 cm of the topsoil out to 15 cm from the tree stem. The removal of the litter destroys the habitat necessary for adults; pruning the lower branches decreases moisture and increases temperatures and air circulation.

Insect: Warren root collar weevil, Hylobius warreni Wood

Distribution: The warren root collar weevil is a common pest in coniferous forests of North America, particularly in the boreal forests of Canada. It is found from Newfoundland to British Columbia, and in southern sections of the Northwest Territories (Cerezke 1994).

Hosts: Jack pine and white spruce are common hosts. In Ontario, the weevil will also attack eastern white, red, and Scots pine, and black and Norway spruce (Cerezke 1994).

Host Damage: The larvae of warren root collar weevil feed on the inner bark of the root collar and roots at and below the surface of the duff, causing complete or partial girdling of the stem and roots and open

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wounds in the root collar area. Profuse resin

flows are associated with the larval wounds. Adult weevils ascend the tree at night to feed on needles, branches and twigs (Cerezke 1994).

Completely girdled trees die. In partially girdled trees, the open wounds may provide portals of entry for secondary pathogens and insect pests. Mature trees subjected to repeated attacks show some loss of growth in height and radial increment and are subject to blow down (Ives and Wong 1988).

Habitat: The presence of the weevil correlates well with site conditions. This weevil prefers trees growing on moist to wet soil and humus conditions and a humus or organic duff layer that is relatively deep, which often includes mosses around the base of the tree (Rose et al. 1994; Cerezke 1994). In Ontario, jack pine stands that are rated as fresh and moist and which support twinflower, lily-of-the-valley, bunchberry, bracken fern, Labrador tea, and leather leaf are likely to be the most susceptible to the weevil. Generally, the abundance of weevils increases with stand age and tree size. Forest Management Guidelines and Recommendations Cerezke (1994) summarized the literature on the Warren root collar weevil and provided guidelines to manage this weevil. The

prescriptions outlined here are based on those guidelines. Before planting, evaluate the site for weevil hazard. Site conditions rated from intermediate to moist and with moderate to high productivity in white spruce and jack pine provide the highest risk for damage by the weevil. Use site-specific plant association information before harvesting and planting. Assessment of the risk to young regeneration may require a pre-harvest survey.

Weevil infested trees left after harvesting will provide a source of weevils for the new plantation. These brood trees include residual trees left from logging, seed trees, windbreak trees, wolf trees, or any other tree that is infested and left on site. Choose uninfested trees as seed trees and remove infested trees whenever possible. If the pre-harvest weevil density is high, a 2 to 3 year post-harvest delay before replanting may reduce weevil damage. Although field studies are lacking, there is good evidence to support the logic of scarifying or burning an area within a year of clear-cut harvesting to increase the mortality of larvae and pupae remaining in cut stumps and adults remaining in the harvested area. Larvae are able to continue their development in stumps for 2 years after cutting. These treatments should also retard the re-invasion and spread of adults for several years after harvest within young stands.

Mixtures of conifers with non-host conifer species (e.g., Tamarack) or deciduous species may retard the invasion of the weevil but again, field experiments to investigate this are lacking. Mixing susceptible species (e.g., jack pine) with less susceptible species (e.g. upland black spruce) is not recommended because the weevils attack the more susceptible species first and, as the populations build up, they attack the less

Warren's root collar weevil damage

78

susceptible species in greater numbers than usual.

Where the weevil is present, pre-commercial thinning or spacing should be delayed beyond 15-20 years to minimize weevil-caused mortality and growth loss. Thinning of sites where Armillaria root rot and the weevil are present should be delayed as long as possible or they should not be thinned at all.

If direct control is deemed necessary, then consider pruning the lower branches (up to 1 m above the ground) and scraping the litter and about 5 cm of the topsoil out to 15 cm of the tree stem to reduce the habitat favourable for the weevil. This practice should be done when trees are between 5 and 15 years old.

References Cerezke,H.F.1994. Warren rootcollar weevil,

HylobiuswarreniWood(Coleoptera:Curculionidae), in Canada: ecology, behavior, damage relationships, and management. The Canadian Entomologist 126: 1383-1442

Ives, W.G.H.;Wong, H.R. 1988. Tree and

shrub insects of the prairie provinces. Edmonton, Alberta. Canadian Forestry Service, Northern Forestry Centre. Information Report NOR-X-292.


1999. Insects of Eastern Pines. Ottawa, ON, Natural Resources Canada, Canadian Forest Service.

Rose, A.H.; Lindquist, O.H. revised by

Syme, P. 1994. Insects of eastern spruces, fir and hemlock. Ottawa, ON, Natural Resources Canada, Canadian Forest Service.

Wilson, L.F.;Millers, I. 1983. Pine root collar

weevil - its ecology and management. Washington, D. C. U.S. Department of Agriculture. Technical Bulletin 1675. 34 p.

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Insect: Pine engraver Ips pini (Say) Distribution: The pine engraver is one of the most common and widely distributed bark beetles (Scolytidae) in North America. It occurs throughout Canada and across the northern United States in the east from the southern Appalachian Mountains northward and in the west along the Rocky mountains to northern Mexico. Hosts: In eastern Canada and the United States, the principal hosts include jack, red and eastern white pines. In western Canada and United States, ponderosa, lodgepole, jack, shore and Jeffrey pines are attacked. Other species of pine are attacked less frequently attacked and probably any species of pine could be a host at some time. Host damage: Adult male beetles initiate attack by boring into the outer bark of the tree and excavating a chamber, called a nuptial chamber. The males release a pheromone to attract an average of three females and after mating, the females bore a gallery in the phloem layer to deposit their

eggs. After hatching, the larvae mine the phloem laterally from the egg gallery. The larval galleries essentially girdle the tree causing a reduction in nutrient and water flow. The foliage of infested trees eventually fades and the trees that were living prior to attack, die.

Habitat: The engraver is seldom a tree killer. Typically, the engraver beetle attacks logging slash, wind-thrown trees, or trees broken by wind, snow or freezing rain. Unthrifty and stagnant stands are particularly susceptible to attack and vulnerable to damage. Populations can build up in slash, and because the beetle often has two or more generations per year (two is normal for Ontario), subsequent populations can attack standing green trees. The tops of standing green trees may be killed while others may suffer complete mortality. Forest Management Guidelines and Recommendations: The following recommendations are based on the publications by Thomas (1957), Kegley et al. (1997) and Overhulser (1999). Maintaining vigourous and healthy forests and sanitation are the keys to preventing tree damage. Slash or weakened trees attract beetles and provide suitable conditions for populations to establish, build up and potentially damage or kill standing green trees. The diameter of the slash and the time it is produced are important considerations. Slash less than 8 cm in diameter can be left behind because it usually dries out rapidly and seldom produces large beetle populations. For slash larger than 8 cm in diameter, the time of cutting is important. Slash created in late summer to late fall, before snowfall, will usually dry out to the point that it is unsuitable for the pine engraver the following year. However, logging slash created from early winter through late spring provide an ideal habitat for the engraver beetle. If possible, avoid cutting during this period but if this is impractical then implement one of the following precautions:

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1) Scatter the slash into open areas to accelerate drying, or crush the slash with heavy equipment. Chipping the slash into small pieces will also reduce the amount of breeding material for the beetles, or, 2) Produce a continuous supply of fresh slash during July and August (the time when the second generation of adults are searching for sites to lay eggs). New slash should be produced when the first generation adults are in the pupal stage. Producing a continuous supply of new slash, called a �green chain� diverts the beetles away from the remaining leave trees. An alternative to the �green chain� is to create large piles of slash in the spring before beetle flight. These slash piles should be at least 3m long and 3m high; leave them in the thinned stand. The pieces in the interior of the pile remain fresh and attractive long enough for the second generation beetles and again divert them away from the standing trees. References Kegley, S.J.; Livingston, R.L.; Gibson, K.E.

1997. Pine engraver, Ips pini (Say) in the Western United States. United States Department of Agriculture, Forest Insect and Disease Leaflet 122. 6 pp.

Overhulser, D. 1999. Pine engraver beetle

(Ips pini). Forest Health Note, April 1999, Oregon Department of Forestry, Oregon. USA. 4 pp.

Thomas, J.B. 1961. The life history of Ips

pini (Say) (Coleoptera: Scolytidae). The Canadian Entomologist 93: 384-390

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Insect: Yellowheaded spruce sawfly, Pikonema alaskensis (Rohwer) Distribution: Yellowheaded spruce sawfly occurs across Canada and the northern United States and follows the distribution of spruce throughout North America. Hosts: The sawfly feeds on all spruces native to North America, including white, black and red and on the exotic - Norway spruce. There appears to be geographical variation in host preference, which may be associated with the synchrony between bud burst and emergence of females (Pointing 1957). White spruce buds burst about 10 days before black spruce (Blais 1957). In Ontario, the sawfly may select one species over the other in areas where both are present (Pointing 1957), whereas in Minnesota, in spite of the abundance of black spruce, white spruce is the common host (Houseweart and Kulman 1976). Host damage: Early instar larvae skeletonize new needles; as the larvae grow, they consume whole needles. Late instar larvae may attack foliage from previous years (Wilson 1971). The yellowheaded spruce sawfly causes severe defoliation of young spruce trees

grown in plantations and in open areas. The susceptible period is usually from three to five years after planting until crown closure

(Kulman 1971). While severe feeding injury may result in the death of branches and whole trees, some trees have been observed to withstand 100 percent defoliation. Mortality in white spruce plantations in Minnesota was 2.3 to 2.7 percent as a result of defoliation by the sawfly, with pockets where mortality reached 15% (Morse and Kulman 1984b). The major economic losses are attributable to reduced growth. Terminal and shoot lengths are shortened relative to the degree of defoliation. Kulman (1971) reported that a single defoliation of 80% or more on 1.5 to 2.5 m tall trees caused about 60% reduction in terminal shoot elongation in the first and 50% in the second year. Two years of similar defoliation caused about an 80% reduction in growth. Long term effects of defoliation have not been examined. Habitat: Young, open-grown trees are preferred (typically 1 to 6 m tall and 5 to 9 years old), especially those in plantations, shelterbelts, and urban ornamental plantings (Wilson 1971; Rose et al. 1994). Population outbreaks often occur on south facing slopes before crown closure (Morse and Kulman 1986). Once trees reach crown closure, sawflies are seldom a problem. Trees grown under an overstory (often aspen) or those in dense stands are generally not susceptible to the sawfly. Forest Management Guidelines and Recommendations Because the sawfly prefers open-grown trees, once crown closure has been achieved in the stand, sawflies are seldom a problem. Therefore silvicultural practices to manage the yellowheaded spruce sawfly should involve full stand stocking, early crown

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closure, or using nurse crops to provide shade. It is always best to grow spruce on sites appropriate for the species. Insect problems are usually more frequent and more severe when tree species are planted �off-site�. Avoid establishing white spruce plantations on south-facing slopes where trees are under greater stress and often have higher insect populations (Morse and Kulman 1986). Also avoid sites for white spruce that have poor drainage or heavy clay soils (Cook 1976 in Katovich et al. 1995). During site preparation, attempt to minimize the loss of soil organic matter and nutrients from planting sites because trees growing on nutrient poor sites are more likely to sustain significant damage if defoliated (Katovich et al. 1995). Site disturbance may also reduce populations of small mammals and insects that feed on sawfly cocoons and keep populations at low levels (Katovich et al. 1995). Therefore, allow some woody material to remain on the site to provide habitat for them. Consider growing white spruce under a light overstory or �nurse� crop because these trees are less susceptible to damage by the sawfly (Morse and Kulman 1984a). A nurse canopy of aspen or white birch, which reduces full sunlight by 25 to 30 percent, not only permits maximum height growth of young spruce but also protects them against spring frost damage (Rauscher 1984). If possible, keep a light overstory of aspen or other species, until trees are about 3 to 4 m tall. Plant at a 2 m by 2 m spacing to encourage early crown closure. If the initial survival in the plantation is poor, then replant to fill in the spaces to promote early crown closure. Avoid overstocking; it may result in slower growth or reduce the ability of the trees to

recover from defoliation or other induced stress. Pre-commercial spacing, which opens up the stand, may encourage the reestablishment of sawfly populations. Be careful with release treatments. Morse and Kulman (1984a) released white spruce from a 70% overstory that was predominantly aspen and observed a six-fold increase in the amount of defoliation by the sawfly the following year compared to the unreleased control. However, Kostyk et al. (1997) did not find an increase in defoliation of black or white spruce by the sawfly after mechanical and chemical conifer release treatments. They noted, however, that even though the vegetation cover was significantly lower in the treatment areas, even a small amount of cover left on the site may deter the sawfly from laying eggs in the released areas. Little is known about the effects of fertilization on yellowheaded spruce sawfly. Popp et al. (1986) fertilized white spruce at 0, 224 or 448 kg/ha of ammonium nitrate and observed that the highest survival of sawfly larvae occurred at 224 kg/ha. This result seems to suggest that there is an optimal level of nitrogen that maximizes the larval survival. More work needs to be done to firmly establish this relationship between fertilization with nitrogen and the response of the yellowheaded spruce sawfly. One common observation is that defoliation by the sawfly tends to be higher when soil nutrients are low, particularly nitrogen (Katovich et al. 1995). Insects may compensate for lower quality food (i.e., lower nitrogen levels) by eating more (Mattson and Scriber 1987), which may explain why defoliation is higher on nitrogen-poor soils (Katovich et al. 1995).

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No efforts have been made to select spruce that are resistant to or tolerant of damage by this sawfly. Nienstaedt and Teich (1972) observed differences in defoliation among 28 white spruce seed sources from Minnesota when infestations were light, but no differences were observed when the same seed sources were heavily defoliated. Connor et al. (1982) found no significant differences in susceptibility of 25 white spruce seed sources to the sawfly when the sawflies were caged on trees. However, the fact that only three trees per seed source were used in this study make it difficult to detect subtle seed source differences (Katovich et al. 1995). References Blais, J.R. 1957. Some relationships of the

sprucebudworm,Choristoneura fumiferana (Clem.) to black spruce, Picea mariana (Moench) Voss. The Forestry Chronicle 33: 364-372

Connor, M.D.; Houseweart, M.W.; Kulman,

H.M. 1982. Susceptibility of white spruce seed sources to yellowheaded spruce sawfly,Pikonemaalaskensis,(Hymenoptera:Tenthredinidae).GreatLakes Entomologist 15: 207-211

Cook, J.L. 1976. Soil and site influences

affecting the defoliation patterns of the yellowheaded spruce sawfly. University of Minnesota. M.Sc. Thesis. 64p.

Houseweart, M.W.; Kulman, H.M. 1976.

Life tables of the yellowheaded spruce sawfly,Pikonemaalaskensis(Rohwer) (Hymenoptera:Tenthredinidae)in Minnesota. Environmental Entomology 5: 859-867

Katovich, S.A.; McCullough, D.G.; Haack,

R.A. 1995. Yellowheaded spruce sawfly- its ecology and management.

St.Paul, Minnesota. North Central Forest Experiment Station. General Technical Report NC-179. 24 p.

Kostyk,B.;Greifenhagen,S.;Bell, F.W. 1997.

Effects of alternative conifer release treatments on yellowheaded spruce sawfly defoliation. Sault Ste. Marie, Ontario. Ontario Forest Research Institute, Ministry of Natural Resources. Forest Research Note 57. 4 p.

Kulman, H.M. 1971. Effects of insect

defoliation on growth and mortality of trees. Annual Review of Entomology. 16: 289-324.

Mattson, W.J.; Scriber, J.M. 1987.

Nutritional ecology of insect folivores of woody plants: nitrogen, water fiber and mineral considerations. pp 105-146. in F Slansky, JG Rodriquez (Eds). Nutritional ecology of insects, mites and spiders. New York, NY: John Wiley

Morse, B.W.; Kulman, H.M. 1984a. Effect

of white spruce release on subsequent defoliation by the yellowheaded spruce sawfly, Pikonema alaskensis(Hymenoptera:Tenthredinidae). The Great Lakes Entomologist 17: 235-237

Morse,B.W.; Kulman,H.M.1984b.

Plantation white spruce mortality: estimates based on aerial photography and analysis using a life-table format. Canadian Journal of Forest Research 14: 195-200

Morse, B.W.; Kulma, H.M. 1986. A method

of hazard-rating white spruce plantations for yellowheaded spruce sawfly defoliation. Northern Journal of Applied Forestry 3: 104-105

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Nienstaedt, H.; Teich, A. 1972. The genetics of white spruce. Washington, D.C. U.S. Department of Agriculture, Forest Service. Research paper WO-15. 24 p.

Pointing,P.J.1957.Studies on the comparative

ecology of two sawflies Pikonema alaskensis Roh and Pikonema dimmockii Cress. (Tenthredinidae, Hymenoptera). University of Toronto. Ph.D. Dissertation. 148 p.

Popp, M.P.; Kulman, H.M.; White, E.H.

1986. The effect of nitrogen fertilization of white spruce (Picea glauca) on the yellow-headed spruce sawfly (Pikonema alaskensis). Canadian Journal of Forest Research 16: 832-835

Rauscher, H.M. 1984. Growth and yield of

white spruce plantations in the Lake States (a literature review). St. Paul, Minnesota. U.S. Department of Agriculture, Forest Service, North Central Forest Experiment Station. Research Paper NC-253. 46 p.

Rose, A.H. Lindquist OH, revised by Syme

P. 1994. Insects of eastern spruces, fir and hemlock. Ottawa, ON. Natural Resources Canada, Canadian Forest Service.

Wilson, L.F. 1971. Yellow-headed spruce

sawfly (revised). Washington, D. C. United States Department of Agriculture Forest Service. Forest Pest Leaflet 69. 3 p.

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Insect: Redheaded pine sawfly, Neodiprion lecontei (Fitch)

Distribution: The redheaded pine sawfly is found throughout most of eastern North America. In Canada, it is found in Ontario, Quebec, and New Brunswick. The sawfly is probably the most serious pest of red pine plantations in southern and central Ontario, and south central Quebec (Rose et al. 1999). Hosts: In Ontario, jack, red and Scots pine are the principal hosts. Larvae will occasionally be found feeding on eastern white pine, but this is almost always the result of larvae migrating from nearby hard pines. Host preference appears to vary with latitude and the availability and abundance of the different pine species (Wilson et al. 1992). In Ontario, red pine appears to be preferred over jack pine, but in the Lake States, jack pine is preferred over red pine. Controlled experimental studies of host preferences have not been undertaken and so that these apparent regional differences may also be a function of host and site interaction. Host damage: Young larvae skeletonize the needles and older larvae consume the entire needle. After the older needles have been consumed, feeding continues on the new growth. As foliage becomes scarce, larvae

feed on the young bark. When a tree has been completely defoliated, larvae migrate to another tree to continue feeding. Complete defoliation is usually enough to kill red and jack pine. Heavy defoliation causes top kill and forking while less extensive feeding stunts height and diameter growth. Branches that are completely defoliated often die. Typically a wide range of defoliation is observed in a single plantation and it is not unusual to see entire trees stripped of foliage. Habitat: Redheaded pine sawfly typically attacks young open-grown trees up to 6 m tall. It can be found in natural stands, plantations and on ornamentals. Once crown closure occurs, the insect is seldom present or its damage significant. Forest Management Guidelines and Recommendations Selecting the right site for a new plantation is probably the most important silvicultural practice for reducing the impact of the redheaded pine sawfly. The condition of the site affects the condition of the trees, which in turn determines the degree of susceptibility to the sawfly. Averill et al. (1982) examined different site conditions for red pine and developed three site classes for resistance to the sawfly. Based on this classification and other ecological information, Wilson et al. (1992) developed management guidelines for red pine. The recommendations below are largely drawn from these guidelines. Jack pine grown under similar conditions as red pine have not shown similar site resistance classes. Grow pine on sites that are appropriate for the species. Sawfly problems are usually more frequent and more severe when tree

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species are planted �off-site�. Site conditions that are poor for tree growth are favourable for redheaded pine sawfly. Trees that are stressed show poor height growth, poor form and off-colour foliage. Avoid planting red pine in high stress sites such as those where there is competition from bracken fern (Pteridium aquilinum (L.) Kuhn) or sod, along edges where there are hardwoods roots, or in frost pockets. Also avoid planting where the soils are nutrient poor, fine textured, too shallow, too compacted, too dry or too moist, or on eroded soils. Sites where the pH is neutral or higher tend to be more susceptible. Sites that are too moist can be indicated by the presence of sedges, even during dry periods. Bracken fern and sweetfern (Comptonia peregrina (L.) Coult.) stress red pine by competing for moisture making them more susceptible to the sawfly. Therefore plant on good sites where competitive species like bracken fern and sweetfern are less than 10% of the ground cover. In general, pines (like all tree species) should be planted on the best sites for the species to keep them vigourous and as stress-free as possible. Good red pine sites that are highly resistant to redheaded pine sawfly have relatively undisturbed soil and have a visible leaching (Ae) zone. These soils also frequently have a B-horizon, containing textured bands or well-developed colour-band (Wilson et al. 1992). Soils should be well-drained, deep, loose loamy sand or gravel and have sufficient water-holding capacity. Remove hardwoods before planting pine on the site. If this cannot be done, then plant at least 6 m beyond the crowns of hardwoods, reducing the competition from hardwoods for moisture and nutrients. Control of competing vegetation may be required to accelerate crown closure and reduce tree stress.

In the Lake States, the recommendation is to avoid planting red and jack pine mixed in a stand or as adjacent blocks of trees because jack pine appears to be more susceptible than red pine to the sawfly. The sawfly tends to cause much more injury to red pine when it is mixed with, or adjacent to, jack pine stands. In Ontario, the sawfly has been a problem mainly in red pine plantations, predominantly in southern Ontario, but this may be a result of host availability rather than host preference because jack pine is scarcer in southern Ontario than red pine. Plant at a 2 m by 2 m spacing to encourage early crown closure. If the initial survival in the plantation is poor, then replant to fill in the spaces to promote early crown closure. Avoid overstocking because it may result in slower growth or loss of the ability of the trees to recover from defoliation or other induced stress. (Griffiths 1958) found that open-grown red pine was more susceptible to the sawfly than shaded trees, whereas (Benjamin 1955) found the reverse for red and jack pine. This apparent contradiction may be more a function of site quality, root competition, or plant stress than overhead shading per se. Once crown closure has been achieved, the redheaded pine sawfly is seldom a problem. Pre-commercial spacing, which re-opens the stand, may result in the reestablishment of sawfly populations. No efforts have been made to select trees that are resistant to the sawfly. In Ontario, tree improvement programs are active for jack but not for red pine. (Hodson et al. 1982) found variation in the incidence of attack by the sawfly among 30 jack pine seed sources obtained from various locations in Michigan, Wisconsin and Minnesota.

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References Averill, R.D.; Wilson, L.F.; Fowler, R.F.

1982. Impact of the redheaded pine sawfly (Hymenoptera: Diprionidae) on young red pine plantations. The Great Lakes Entomologist 15: 65-91

Benjamin, D.M. 1955. The biology and

ecology of the red-headed pine sawfly. Washington, D.C. U.S. Department of Agriculture Forest Service. Technical Bulletin 1118. 57 p.

Griffiths, K.J. 1958. Host tree preferences of

adults of Neodiprion lecontei (Fitch). Ottawa,ON. Department of Agriculture, Forest Biology Division. Bi-monthly Progress Report Vol. 14, No. 5. p.1.

Hodson, A.C.; French, D.W.; Jensen, R.A.;

Bartelt, R.J. 1982. The susceptibility of jack pine from Lake States seed sources to insects and diseases. St. Paul, Minnesota. USDA Forest Service, North Central Forest Experiment Station. NC-225. 12.


1999. Insects of Eastern Pines. Ottawa, ON, Natural Resources Canada, Canadian Forest Service.

Wilson,L.F.;Wilkinson, R.C. Jr.; Averill,R.C.

1992. Redheaded pine sawfly: its ecology and management. U. S. Department of Agriculture Forest Service. Handbook 694. 53p.

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Insect: Forest tent caterpillar, Malacosoma disstria Hübner Distribution: The forest tent caterpillar is found from coast to coast across Canada from the tree line to the southern United States (Rose et al. 1997). Hosts: The caterpillar attacks almost all hardwood trees, with red maple being a notable exception (Rose et al. 1997). Trembling aspen, balsam poplar, white birch and sugar maple are common hosts in the boreal and Great Lakes-St. Lawrence regions of Ontario. It will even eat tamarack during outbreaks. Host Damage: Forest tent caterpillar larvae feed in clusters on foliage. Larvae begin feeding about the same time as the leaves unfold. As foliage becomes scarce, larvae move around the tree in search of food.

When a tree has been completely defoliated, larvae will migrate to another tree or surrounding deciduous vegetation to continue feeding (Rose et al. 1997). Trees are rarely killed because they can produce a second crop of leaves in midsummer following defoliation. Light defoliation causes little damage but moderate-to-heavy defoliation, especially over two or more years, causes a decrease in radial growth. Vigourous trees can tolerate up to 2-3 years of heavy defoliation without

suffering serious growth loss or mortality. Growth recovery to pre�infestation levels may take two to three years after the caterpillar population collapses. Trees heavily defoliated for four or more years, may suffer branch mortality and some trees may die. Trees stressed from drought are less tolerant of defoliation and may die sooner. Defoliation does weaken trees and makes them more susceptible to attack and vulnerable to damage by woodborers, cankers and root rots. Infestations of forest tent caterpillars are widespread and cyclic, occurring every 6-16 years and lasting 4-5 years (Ives and Wong 1988). Habitat: This insect occurs over a wide variety of habitats because it has a large geographic and host range. Forest Management Guidelines and Recommendations The wide host range of the tent caterpillar (all hardwoods except red maple) severely limits forest management options. Typically, growth losses are accepted. After a few years, natural control factors such as weather, starvation, parasites, predators, and disease substantially reduce populations of forest tent caterpillar. Recent studies by Roland (1993), Roland and Kaupp (1995), Roland and Taylor (1997), Roland et al. (1997, 1998) have examined the effects of forest fragmentation, forest stand size and the dynamics of insects and diseases. Roland (2002, and personal communication, April 2002) recommends that forest managers not fragment the forest, creating stands of less than 100 ha. Distance between stands is less of a factor if the leave blocks are a minimum 100ha, but obviously the closer together large blocks are, the larger the intact forest. Minimizing stand edge would be preferable.

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References Ives, W.G.H.; Wong, H.R. 1988. Tree and

shrub insects of the prairie provinces. Edmonton, Alberta. Canadian Forestry Service, Northern Forestry Centre. Information Report. NOR-X-292.

Roland, J. 1993. Large-scale forest

fragmentation increases the duration of tent caterpillar outbreak. Oecologia 93: 25-30

Roland, J. 2002. Press release, 12 March,

2002. Available at http://www.eurekalert.org/pub_releases/2002-03/noco-tca031202.php

Roland, J.; Kaupp, W.J. 1995. Reduced

transmission of forest tent caterpillar NPV at the forest edge. Environmental Entomology 24: 1175-1178

Roland, J.; Mackey, B.G.; Cooke, B. 1998.

Effects of climate and forest structure on duration of forest tent caterpillar outbreaks across central Ontario, Canada. The Canadian Entomologist 130: 703-714

Roland, J.; Taylor, P.D. 1997. Insect

parasitoid species respond to forest structure at different spatial scales. Nature (London) 386: 710-713

Roland, J.; Taylor,P.D.; Cooke, B. 1997.

Forest structure and the spatial pattern of parasitoid attack. Forests and insects. AD Watt, NE Stork , MD Hunter. New York, Chapman and Hall: 97-106.

Rose, A.H.; Lindquist,O.H.; Nystrom, K.L.

1997. Insects of eastern hardwood trees.

Ottawa, ON. Natural Resources Canada, Canadian Forest Service. Forestry Technical Report. 29. 304 p.

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Disease: Armillaria root rot, Armillaria ostoyae (Romagn.) Herink Distribution: Occurs worldwide in boreal, temperate, and tropical forests (Hood et al, 1991); very common throughout Canada and the United States. Host: Capable of affecting a wide variety of tree species. Host Damage: Armillaria consists of a group, or complex of species and strains, that differ in pathogenicity and host preference (Dumas 1988). The fungis normally lives saprophytically on dead woody material but often becomes parasitic when the overall vigour of the host declines as a result of unfavourable environmental conditions, particularly drought. The disease generally causes a rot in the roots and base of the stem, reducing tree vigour and growth rate, but it will also influence forest succession by killing seedlings, saplings, and sometimes mature trees. Trees die individually or in small circular pockets, especially in monocultural plantations. In mature and over-mature forests the disease may occur over very large areas, and in the plantations that replace these heavily infected sites numerous small disease centers routinely develop.

The first symptoms of infection are yellowing of foliage, loss of old needles, and the death of branches in the upper tree crown. All foliage may die suddenly on smaller trees. White mycelial fans form under the bark of the roots and root collar, and are often associated with basal resinosis. Dark brown to black shoe-string-like structures called rhizomorphs are often found on the stump and roots and in the soil surrounding the infected trees. The rhizomorphs consist of a dark brown outer layer of closely compacted fungus tissue. The disease spreads primarily through root grafts and rhizomorphs, growing outward through the soil from infected roots and penetrating the roots of adjacent trees. The fungus kills the cambium and outer layers of wood, causing decay. Tree mortality results when the fungus has girdled the major roots and root collar. Incipient decay is usually yellowish-brown in colour and the wood has a water soaked appearance. Advanced decay is yellowish in colour, with numerous black zone lines, and is soft and stringy in texture. The disease usually does not progress upward into the stem for more than a meter. Clusters of honey-coloured mushrooms are produced at the base of infected trees and stumps in early autumn. Basidiospores are wind-borne and generally infect stumps or dead trees. Occasionally living trees are infected through open wounds at the base of the tree, or on exposed roots. Forest Management Guidelines and Recommendations Armillaria root rot is the most serious root disease in Ontario, capable of attacking both deciduous and coniferous trees in natural forests and plantations. Among conifers, pine species are considered more susceptible than

Rhizomorphs of Armillaria root rot

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spruce, although spruce on upland sites is also affected by this disease (Whitney 1988). Armillaria root rot is very difficult to control and can persist on logged sites for more than ten years. Roth et al. (1979) and Shaw and Calderon (1977) have reported that armillaria can cause significant losses in conifer plantations converted from hardwood, although the pre-harvest level of root rot is probably more critical than the pre-harvest tree species. In stands known to have a history of the disease, colonization of stumps can result in significant losses to the future stand. In areas destined to be high-value conifer plantations, a pre-harvest survey to determine the prevalence of root rot is recommended. Careful site selection and good management practices that maintain a healthy, vigourously growing stands are strongly recommended. When a site is found to have a high source of inoculum, site preparation and stump removal (Morrison and Mallett 1996) should be considered. Stump removal followed by a short fallow period has helped to reduce secondary inoculum, especially on sites that originally consisted of overmature conifers. Although costly, the removal of old, infected stumps, and root raking should be considered, especially if the areas to be replanted are to be used as seed orchards or for high value production Scarification can sometimes exacerbate root disease problems by distributing uninfected material across a site (Ronnberg and Vollbrecht 1999). Infection centers within existing plantations are extremely difficult to control. The root systems of adjacent trees around an infection center may already be infected and if these trees are cut down in an attempt to stop the spread, the disease very quickly colonizes their entire root systems causing the epicenter to rapidly expand. Both

precommercial and commercial thinning can increase the damage level caused by Armillaria and should be avoided around armillaria pockets. Stanosz and Patton (1987) noted the potential for armillaria to accumulate in dead root systems after repeated rotations. Both armillaria and tomentosus require food bases such as stumps or roots for the fungus to grow and infect other trees (Stanosz and Patton 1990) the long-term effect of shorter rotations with continual planting is unknown. However, the literature would suggest that shorter rotations could seriously increase root rot. Heavily infected trees experience radial growth loss, butt rot, and are prone to wind throw because of their weakened root systems Planting these sites with the proper species and healthy stock is probably most important. For example, conifer seedlings are most susceptible to armillaria during stand establishment, particularly if stressed, or if the roots are deformed by the greenhouse production process or during planting (Livingston 1990). In such instances, seeding might be a cost-effective alternative, which could result in reduced losses. The planting of less susceptible species or using locally adapted seed sources for indigenous species, matching site conditions and type is strongly recommended and will help to avoid economic losses (Haggle and Shaw 1991).

References Davis, C.; Meyer, D. T. . 1997. Field guide

to tree diseases of Ontario. Nat. Res. Can., Canadian Forest Service,Great

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Lakes For. Centre, Sault Ste Marie, ON. NODA/NFP Tech Rep. TR-46. 135 p.

Dumas, M.T. 1988. Biological species of

armillaria in the mixed-wood forest of northern Ontario. Can. J. For. Res. 18: 872-874.

Hagle, S.K.;Shaw, C.G. 1991. Avoiding and

Reducing Losses from Armillaria Root Disease. In: Armillaria Root Disease, 157-173. ed. Charles G. Shaw and Glen A. Kile. U.S. Dept. of Agric. U.S. For. Serv., Agric. Handbook No. 691. 233 p.

Hood, I.A.; Redfern, D.B;.; Kile, G. A..

1991. Armillaria in Planted Hosts. In: Armillaria Root Disease,: 122-149. ed. Charles G. Shaw and Glen A. Kile. U.S. Dept. of Agric. U.S. For. Serv., Agric. Handbook No. 691. 233 p.

Livingston, W. 1990. Armillaria ostoyae in

young spruce plantations. Canadian Journal of Forest Research 20: 1773-1778.

Morrison,D.; Mallett,K.1996. Silvicultural

management of armillaria root disease in western Canadian forests. Canadian Journal. Plant Pathology. 18: 194-199.

Ronnberg, J. ; Vollbrecht., G. 1999. Early

infection by Heterbasidium annosum in Larix X eurolepis seedlings planted on infested sites. European Journal Forest Pathology 29: 81-86.

Roth,L.F.; Shaw, C.G. III.; McKenzie, M.;

Crockett, F. 1979. Early patterns of Armillaria root rot in New Zealand pine plantations coverted form

indigenous forest � an alternative interpretation. New Zealand Journal Forest Science 9: 316-323.

Shaw, C.G. III.; Calderon, S. 1977. Impact of

Armillaria root rot in plantations of Pinus radiata established on sites converted from indigenous forest. New Zealand Journal Forest Science 7: 359-373.

Stanosz,G.R.;Patton,R.F.1987. Armillaria

root rot in aspen stands after repeated short rotations. Canadian Journal Forest Research 17: 1001-1005.

Stanosz, G.R.; Patton, R.F. 1990. Stump

colonization by Armillaria in Wisconsin aspen stands following clearcutting. European Journal Forest Pathology. 20: 339-346.

Whitney, R.D. 1988. Armillaria root rot

damage in softwood plantations in Ontario. For. Chron. 64:345-351.

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Disease: White pine blister rust, Cronartium ribicola J.C. Fischer

Distribution: The blister rust is widespread in Canada across range of eastern and western white pine Host: All native five needle pine, especially eastern (Pinus strobus) and western (Pinus monticola) white pine; alternate hosts include all domestic and wild currants and gooseberries (Ribes spp.). Host Damage: White pine blister rust is native to Asia, but was first introduced into North America from Europe, in 1906 on German nursery stock. The disease was introduced to British Columbia in 1910, and to Ontario and Quebec in 1911 and is now considered the most damaging disease of eastern white pine in Canada. White pine blister rust requires two different hosts to complete its life cycle (Ziller 1974). Infection takes place through the needles on the pine host, late in the summer. During the next 12-18 months the fungus grows back along the twig and branch towards the main stem. Yellowish to orange discolouration of the bark tissue of the branch during the second or third year of infection. The spindle-shaped cankers that form, eventually girdle the branch or main stem, and everything distal to the canker dies. In the late summer of the third year of infection, honey-coloured or brownish droplets of liquid exude from the swelling. The following spring, white blisters, which cover orange coloured spore masses, erupt through the bark, and the aecial spores are dispersed, infecting the leaves of the secondary host, Ribes spp.. Throughout the summer, uredial spores are produced on the underside of the Ribes leaves in yellowish to light orange coloured pustules. These uredial spores are only capable of re-infecting other ribes

plants. Several generations of these spores are produced in the summer and serve to

spread and intensify the infection on the ribes

plants. Late in the summer or early fall, telial spores are produced on the underside of the Ribes leaves in short, brownish, horn-like structures. These spores germinate in place and produce the basidial spores that are released, and re-infect nearby pines. Forest Management Guidelines and Recommendations White pine blister rust has specific temperature and moisture requirements for successful infection (Van Arsel et al. 1956). Based on these criteria, hazard zones have been developed for growing white pine in Ontario and Quebec (Gross 1985; Lavellée 1974). White pine grown in traditional plantations within high hazard zones usually suffer serious mortality during its early years, especially if Ribes is in close proximity (Lavellée 1992). However, even within a high hazard area, white pine production is possible. Avoid planting eastern white pine in areas where the alternate host is known to be abundant. Resistant varieties of white pine have been developed and should be used in high risk areas, if suitable stock is available. Van Arsdel (1961) recommends that plantings not occur in areas where cold air collects, such as depressions. Surveys conducted in Northeastern Ontario showed

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infection in open grown plantations had much lower infection levels if grown on upper slopes (A. Hopkin unpublished). Some level of control has been achieved by the removal of the alternate host, Ribes spp., within 300 m of a pine plantation. Pruning has also been an effective though labor-intensive tool in reducing blister rust incidence. In high value plantations and seed orchards, the disease can be effectively controlled by hand pruning, and destroying infected branches or severely infected trees. Most infection occurs on the lower branches and over time can result in stem cankers if initial infection is within 10-15 cm of the stem. Pruning the lower branches up to two meters from the base of the stem on young trees (age 5-7 yrs) will dramatically reduce infection by the fungus (Hunt 1991). The pruning of lower branches will open the plantation to air movement, drying the site and reducing the germination rate of the infecting spores. Stand density is also important in reducing infection in plantations. Early thinning is known to increase the incidence of this disease (Hungerford et al. 1982). Hagle et al. (1989) recommended thinning at 25-30 years, which allows for a closed canopy and for the natural thinning caused by the rust. The use of shelterwood systems was suggested by Van Arsdel (1961) as a means of reducing blister rust infection in high hazard areas. The purpose of shelterwood is to maintain drier, and therefore, less conducive conditions for infection on the understory pine. Shultz (1989) describes the use of blister rust tolerant stock in a shelterwood. In the case of white pine blister rust is also affected by spacing when grown on a high hazard area. Maintenance of a closed canopy reduces infection (Van Arsdel 1961). Shelterwood created either by underplanting, or with the use of a fast growing species such as hybrid poplar or

birch, will also deliver the advantages of a closed canopy. References Canadian Forest Service. 1994. Tree

diseases of eastern Canada. ed. D.T. Myren., Nat. Res. Can., Canadian Forest Service, Sci. Sustain. Dev. Dir., Ottawa, ON. 159 p.

Hagle, S.K.; McDonald, G.I.; Norby, E.A.

White pine blister rust in northern Idaho and western Montana: Alternatives for integrated management. USDA. Forest Service, General Technical Report INT-261. 35p.

Hungerford,R.D.; Williams,R.E.; Michael,

M.A. 1982. Thinning and pruning western white pine: a potential for reducing mortality due to blister rust USDA. Forest Service, Research Note INT-322.7p.

Lavallee, A. 1992. The spread of white pine

blister rust in young white pine plantations. Forestry Canada, Information-Report LAU-X-101E. 23 pp.

Schultz, J.R. 1989. Using disease resistant

white pine to meet multiple resource objectives. North. J. Appl. For. 6:38-39.

Van Arsel, E.P. 1961. Growing white pine in

the Lake States to avoid blister rust. USDA Forest Service. Lakes States Forest Experimental. Station. Paper No. 92, 11p.

Van Arsel, E.P. A.J. Riker; R.F. Patton.

1956. The effects of temperature and moisture on the spread of white pine

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blister rust. Phytopathology. 46: 307-317.

Ziller, W.G. 1974. The tree rusts of western

Canada. Environ. Can., Canadian Forestry Service, Ottawa, Ont. Publ. 1329.

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Disease: Scleroderris canker, Gremmeniella abietina (Lagerb.) Morelet Distribution: In North America, two distinct strains of the fungus are referred to as the North American and European races (Skilling et al. 1986) are recognized as damaging to pines. The North American race is found in New Brunswick, Ontario and Quebec, north of 45o N latitude. The European race, first appeared in North America in New York State in 1975, where it killed several thousand hectares of semi-mature red and Scots pine (Skilling 1977). In Ontario, this race was first recorded in 1985; it is restricted to central Ontario in the Huntsville and Bancroft areas. It is also found in Newfoundland and New Brunswick, and much of southern Quebec, where it has caused considerable damage (Lachance and Laflamme 1987). Hosts: North American race - primarily Austrian, jack, red, and Scots pine; occasionally eastern white pine. European race � primarily red pine. Five needle pines seem to be more resistant than the two and three needle group.

Host Damage: The North American race of G. abietina infects young trees under two metres in height. However, it will infect the lower branches of larger trees where the fungus may persist and spread to young trees; this race has been associated with numerous planting failures (Dorworth 1970). The European race causes damage to all age and size classes, and with favourable weather conditions, can spread rapidly through the upper crowns of plantation trees. Both races of scleroderris canker have a similar life history (Skilling et al. 1986). Infective spores are generally dispersed and infect trees during wet periods in the spring and early summer. The North American race produces two types of spores, ascospores, which are capable of long range wind dispersal, and conidia spores, which are dispersed by rain droplets over short distances. The European race produces only conidia spores making long-distance dispersal unlikely. Infection takes place through the base of the needles. The following year infection, symptoms become evident on what are now second year needles. The base of the needles on the tip of infected branches turn red in the early spring. The North American race the fungus grows back along the branch toward the main stem, usually killing a single internode per year. Once the fungus reaches the main stem, it girdles the stem, killing the tree above the point of infection. If the fungus does not completely girdle the tree, a canker results. The European race progresses more rapidly, killing entire branches in just one season. Infection occurs at all heights on the tree and when environmental conditions are favourable for this race of the fungus, mortality can result in a single season. Additional information on the life history and symptomology of this disease is provided by

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Laflamme (1991) and Canadian Forest Service (1994). Forest Management Guidelines and Recommendations Scleroderris canker is climatologically sensitive (Marosy et al. 1989) and does not occur below 44o30� (Hopkin and McKenney 1995). On this basis, hazard zones based on climate have been proposed for Ontario (Venier et al. 1998). When grown in a high hazard zone scleroderris can be controlled through pruning and sanitation (Hopkin and Laflamme 1995). After the disease is detected, and race verified, the prescribed control method is for onsite tree removal and destruction of diseased material, particularly if the European race is present. Pruning trees has shown to be an effective control measure if the disease is at low levels (<5% trees infected). To be effective as a control, pruning should be performed on both healthy and diseased trees in affected plantations. Pruning of the lower third of the crown for all plantation trees is advisable to prevent or reduce the spread of disease. Regardless of tree height, if less than 2% of pines have only one or two infected branches, only the infected branches should be removed. This procedure should be repeated the following year if the disease is still evident. In plantations with trees less than 1.5 m high, only infected branches should be cut or destroyed. In the following year the plantation should be inspected and the procedure repeated if necessary. In plantations with trees over 1.5 m in height, where more than 2% of trees are affected, the lower whorls should be removed up to one whorl above the highest infected branch. If

more than two thirds of the whorls are infected, the tree should be removed and destroyed. If the majority of the trees in the plantation are infected and more than 25% of the trees are dead or severely infected, consideration should be given to complete destruction of the plantation. . Nursery infections, which are often responsible for disseminating the disease, can be significantly reduced by the removal of infected windbreak trees, or the removal of lower branches of susceptible windbreak trees. Fungicide applications have proven to be an effective means of control in nurseries (Hopkin and Laflamme 1995; Skilling et al. 1986) but are not required in nurseries south of the hazard zone. References Canadian Forest Service.1994. Tree diseases

of Eastern Canada. Ed. D.T. Myren. Natural Resources Canada, Can. For. Serv. Ottawa, Ont.

Dorworth, C.E. 1970. Sleroderris lagerbergii

Gremmen and the pine replant problem in central Ontario. Dep. Fisheries and Forests. Can. For. Serv., Sault Ste. Marie, ON. Information Rep. O-X-139 12p.

Dorworth, C.E.; Davis, C.N. 1982. Current

and predicted future impact of the North American race of Gremmeniella abietina on jack pine in Ontario. Environ. Can., Can. For. Serv., Great Lakes For. Res. Cent., Sault Ste. Marie, ON. Inf. Rep. 0-X-342.

Hopkin, A.A.; McKenney, D.W. 1995. The

distribution and significance of scleroderris in Ontario.Canadian Forestry Service, Sault Ste. Marie, ON. NODA/NFP Tech Rep. TR-7. 12p

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Hopkin,A.A.; Laflamme, G. 1995. The

distribution and control of scleroderris disease in Ontario. Front line Tech Note 21. 4p.

Laflamme, G. 1991. Scleroderris canker on

pine. Forestry Canada, Quebec Region, Ste. Foy Quebec, Information Leaflet LFC 3. 12 p.

Laflamme, G. ; Lachance, D. 1987. Large

Infection Centre of Scleroderris Canker (European Race) in Quebec Province. Plant Disease 71:1041B1043.

Manion, P.D. editor, 1984. Scleroderris

canker of conifers. in Proceedings of an international symposium on Scleroderris canker of conifers, Syracuse, New York, June 21-24, 1983. Forestry Science Vol. 13. Martinus Nijhoff/Dr. W. Junk Publishers, The Hague.

Skilling, D.D.; Schneider, B.; Fasking, D.

1986. Biology and control of Scleroderris canker in North America. USDA For. Serv. Res. Rep. NCB275. 18p.

Venier, L.; Hopkin, AA.; McKenney,

D.M.;Yang, Y. 1998. A spatial, climate-determined risk rating for scleroderris disease of pines in Ontario. Can. J. For. Research 28: 1398-1404.

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Disease: Tomentosus root rot, Inonotus tomenetosus (Fr.:Fr.) Teng Distribution: Associated with spruce-pine forests throughout Canada and the United States. Host: The primary hosts are white, black, and Norway spruce. Occasionally eastern white, jack, and red pine, fir, hemlock, and larch. Host Damage: Tomentosus root rot is a native pathogen that infects trees through root grafts and airborne spores. The fungus slowly grows through the roots of the tree towards the stem, eventually killing the tree.

The rot can extend up into the main stem of the tree up to 3 m, resulting in significant volume loss in the butt log. Infected trees first show signs of reduced vigour, reduced leader growth, thinning of foliage, and stressed cone crops. The incipient stage of the disease causes a reddish-brown stain in the central portion of the root wood. Advanced decay consists of the development of pockets in the wood tissue filled with either white or yellow fibers. Infected trees may appear healthy but actually have extensive amounts of advanced decay throughout the base of the stump and butt log and can live for 15 or more years before death occurs. As the disease advances

in the larger structural roots of the tree, they become weakened, and the tree becomes prone to windthrow and blowdown. Stumps of infected trees remain as an inoculum source for several years following harvesting and become a serious problem in second-growth stands. It is estimated that approximately 15% of all living white and black spruce in natural stands, greater than 30 years in age, are infected with tomentous root rot (Whitney 1977). The spread of the disease is enhanced in pure spruce plantations by the presence of the continuous susceptible root mat. Whitney (1993) noted higher proportions of trees were infected in pure white spruce plantations than in natural stands. A survey conducted in a 64-year-old white spruce plantation that was clear cut in 1989, revealed that 58% of the stumps showed evidence of tomentosus root rot and an additional 20% were infected but the disease had not yet reached stump height. In naturally occurring mixedwood stands in the same vicinity only 13% of similar age white spruce were affected and only 10% of these showed any evidence of the decay at stump height. The disease is most prevalent on upland sites with highly acidic soils. A deep duff layer that favours Hylobious root weevils also favours the spread of the disease due to the increase in root wounds (Whitney 1961). Once established, the disease spreads from tree to tree primarily through root grafts. Diseased trees often occur in groups or pockets, resulting in the formation of stand openings. Tan to yellowish-brown fruiting structures, with a velvet-like upper surface, develop on the ground above infected roots or on the trunk of the host in late summer or early fall. The spores from these are wind-borne and can be carried to new areas where infections occur at root or stem wounds.

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Forest Management Guidelines and Recommendations Damage and volume loss caused by tomentosus root rot increases as stands age, due to the increase in infection sites over time. Once a small pocket of the disease has started, additional damage can be expected within 5 years. Whitney (1993) has suggested that thinning can be a useful tool in reducing this disease. The literature on the effect of thinning on root rots is mixed. Thinning can be used to improve stand vigour and hence reduce root rot under normal conditions; however, Morrison (1981) recommends that thinning should not be conducted in heavily damaged stands. Alternatively, Whitney (1993) reported that the incidence of tomentosus root rot was reduced in white spruce plantations through thinning. Guidelines for control have been summarized by Whitney (2000). Early harvesting can reduce losses to this disease and should be considered when losses are unacceptable. Cutting only the trees with above ground symptoms will not stop or prevent the spread of the disease to remaining trees. Heavily infected stands, with one or more stand openings per hectare, should be clear cut and regenerated with less susceptible species, such as hardwoods or pines. If the site is to be replanted to spruce, stump removal and root raking the site should be considered. Site selection is important, moist or alkaline sites pose little hazard to Tomentosus. Planting pure stands of spruce on gravelly, sandy or silty soils should be avoided. On upland sites planting stock carefully to avoid root damage is important in disease avoidance. Maintain a good general overall health by preventing additional stress on the host by other agents, whether it be insect, disease, or human activities.

References Canadian Forest Service 1994. Tree diseases

of eastern Canada. ed. D.T. Myren. Nat. Res. Can., Can. For. Serv., Sci. Sustain. Dev. Dir., Ottawa, ON. 159 p.

Morrison, D.J. 1981. Armillaria root disease:

a guide to disease diagnosis, development and management in British Columbia. Canadian Forest Service, Information Report BC-X-302.

Whitney, R.D. 1961. Root wounds and

associated root rots of white spruce. For. Chron. 37: 401-411.

Whitney, R.D. 1962. Studies in forest

pathology. XXIV. Polyporus tomentosus Fr. as a major factor in stand-opening disease of white spruce. Can. J. Bot. 40:1631-1658.

Whitney, R.D. 1977. Polyporus tomentosus

root rot of conifers. Dep. Fish. Environ., Can. For. Serv., Great Lakes For. Cent., Sault Ste Marie, Ont. Tech. Rep. No. 18. 12 p.

Whitney, R.D. 1993. Damage by tomentosus

root rot in white spruce plantations in Ontario, and the effects of thinning on the disease. For. Chron. 69:445-449.

Whitney, R.D. 2000. Forest management

guide for tomentosus root disease. Ontario Ministry of Natural Resources. 20p.

forest management guidelines for major insects and diseases of

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