Volume 22 No. 5 May 29, 2015

Contents...

Scouting Report

Conifers (As Christmas & Landscape

Trees): Pine Needle Scale,Weir’s Cushion Rust, Ploioderma Needlecast ..................................17

Conifers (As Landscape Ornamentals):

Elongate Hemlock Scale, Juniper Scale ..........................................17

Broad-leaved: Apple Scab, Azalea Leaf/Flower Gall, Azalea Whitefly, Boxwood Leafminer, Four-lined Plant Bug, Honeylocust Plant Bug, Lilac Borer, Native Holly Leafminer, Privet Rust Mite, Rose Leafhopper, Two-spotted Spider Mite White Prunicola Scale ..........................................18

Things to Look For—Arborvitae Leafminer, Bagworms, Bronze Birch Borer, Lophodermium Needlecast, Mountain Ash Sawfly, Oak Spider Mite, Oystershell Scale, Pine Tortoise Scale, Southern Red Mite ........... 19

Feature: Matters of Scale: Wax and Azalea Bark Scales ............... Insert

Growing Degree Days ..............20

Phenology ....................................20

Ploioderma Needlecast (23)—Fruiting bodies of the fungus that causes Ploioderma needlecast on Austrian pine are now readily visible on infected needles. Look for tan to brown needle tips or bands on 2014 and older needles, especially on the lower third to half of the crown. Examine these needles closely for thin black lines about 1 – 5 mm long and running lengthwise along any discolored portion of the needle surface. These are the fruiting bodies. Do not confuse this with red-band (=Dothistroma) needle blight where short, thin dark brown bands lines may be encircling portions of needles that have a reddish-brown appearance. Sporulation of Ploioderma usually begins within a few weeks after the appearance of the fruiting bodies, and with warmer and wetter weather available, they should develop quickly. Unless your area is experiencing a very dry spring, you should expect spore production to begin by the time the new needles begin to emerge from the fascicle. No fungicides are currently registered in New York to manage this disease on landscape trees. In forest tree nurseries and Christmas tree plantations, apply copper hydroxide per label directions.

Conifers(As Landscape Ornamentals Only)

Elongate Hemlock Scale (45)—We recently found a few crawlers of elongate hemlock scale in Westchester County and Long Island. The crawlers are bright, lemon yellow and 0.1mm long. The insect is a serious pest of hemlock and it also attacks yew, spruce, and Douglas-fir. Feeding causes needles to turn yellow and drop prematurely. Treat heavily infested plants in late May through mid-June (360 – 700 GDD50).

Scouting ReportConifers (As Christmas & Landscape Trees)

Pine Needle Scale (47)—We recently found a few tiny red crawlers of this scale now and there were still eggs under the scale covers as well. Scots, mugo and white pine are common hosts. In addition, the scales may affect Austrian and red pines and less often, spruce, Douglas-fir and cedar. Many pesticides are registered for control of this insect but most infestations can be contained with applications of materials like horticultural oil or insecticidal soap at 298 – 448 GDD50. Once the scales have settled and begun to form their protective covers, they will be much more difficult to eradicate and a horticultural oil may be your best management choice. Several treatments may be required because they hatch out over a period of time.

Weir’s Cushion Rust (143)—This needle rust, caused by Chrysomyxa weirii, was sporulating on a Serbian spruce at our scouting site in Orange County last week. Infected needles have conspicuous yellow-orange spots with spore-bearing pustules in the center of each. The spores will be windblown to new needles. Later in the growing season, infected previous year needles are shed from the tree. The disease can infect most spruce species and poses the greatest threat to Colorado blue spruce Christmas trees. However, it will also reduce the value of landscape specimens. To treat, apply a registered fungicide when budbreak is 10 percent or more complete, and make two more applications at 7- to 10-day intervals.

Scots, mugo and white pine are common hosts.

18—Branching Out

Juniper Scale (46)—The yellow eggs of this scale were evident at our scouting sites in Westchester County and Long Island. The yellow crawlers will emerge soon. Light infestations cause no apparent damage, while heavy feeding causes the foliage to turn yellow. Use of a dormant spray is usually enough. In the growing season, do not spray if there is an abundance of parasites and predators. For heavy infestations only, treat crawlers in mid-June to early July (707 – 1260 GDD50).

Broad-leaved Trees and ShrubsApple Scab (42)—The lesions of this common disease, caused by the fungus Venturia inaequalis, are becoming quite obvious now. The lesions are olive green, circular with uneven margins. With time, the lesions enlarge, darken and turn velvety. With heavy infections, the leaves may curl, cup or become dwarfed. Lesions may also be seen on the fruit where they appear as rough, dark green areas. Although the first cycles of the disease have already caused significant infection some protection will be provided by applications of appropriate fungicides starting now.

Azalea Leaf/Flower Gall (124)—Symptoms caused by this fungus from the genus Exobasidium have begun to appear on azalea. The size and shape of the leaf and flower galls vary with the host plant and strain of fungus. Hosts include azalea, mock azalea, bearberry, blueberry, cranberry, huckleberry, mountain laurel, leucothoe, and rhododendron. We suggest that the galls be picked and destroyed but there are fungicide treatments available.

Azalea Whitefly (151)—Adult whiteflies, resembling tiny white moths, have been detected on azalea on Long Island. Hosts of this insect include azalea, rhododendron, mountain laurel, and andromeda. Predators and parasites are frequently effective in keeping these pests at low levels. Rake

up and destroy fallen leaves from infected plants. If infestations are intolerable apply horticultural oil, neem oil or other registered insecticide in early June to Mid-July (448 – 700 GDD50) and again at 1250 – 1500 GDD50 and at 2032 – 2150 GDD50.

Boxwood Leafminer (94)—Boxwood leafminer adults are emerging and can easily be seen flying around infested boxwood shrubs at various scouting sites around the state. They are small orange, gnat-like flies. Adult females lay their eggs in the tender leaf tissue, but the new leaves do not show signs of mining until later in the summer when the larvae are larger. Injury is caused when the larvae feed in the soft leaf tissue. Mined or blistered leaves are evident from midsummer until the leaves are shed from the plant. Where allowable, soil application of imidacloprid via soil injection or drench is very effective. Another management option is to spray with a registered pesticide between 350 – 600 GDD50.

Four-lined Plant Bug (190)—Four-lined plant bug nymphs are active and causing damage. The nymph’s color ranges from bright red to yellow and the forewings on the adult are yellow turning to green. However, the four black stripes remain distinct. Woody ornamentals that serve as food for this insect include azalea, deutzia, dogwood, forsythia, viburnum, weigela, rose amur maple, and sumac. The plant bug also feeds on many herbaceous plants. Feeding injury to upper surfaces of leaves by both nymphs and adults generally takes the form of discrete circular spots that may be visible from above. Injured areas may turn black or become translucent, and after several weeks the remaining necrotic tissue may drop out leaving small holes. On shrubby plants the topmost leaves are the first to be injured.

Honeylocust Plant Bug (194)—The pale green nymphs have emerged and are causing

damage to honeylocust. You can tap the foliage over a white piece of paper and see if any plant bugs fall onto the paper. The unfolding leaflets are very susceptible to damage. The feeding of the nymphs and adults causes these leaves to become stunted, deformed, and chlorotic. With a large population of plant bugs, defoliation is possible. If the growing conditions are adequate, honeylocusts will be able to recover from early damage and refoliate. If needed, treat with horticultural oil or other registered pesticide 58 – 246 GDD50

Lilac Borer (122)—The adults of this clearwing moth (Podosesia syringae) have recently been found in pheromone traps according to Don Gabel from New York Botanical Garden. They are ½ inch long, metallic brownish black in color. Additional hosts include privet, fringetree, and ash. Look at the bark for holes (circular, clean, and ¼ inch in diameter), sawdust, and cracks. A registered pesticide should be applied in mid-May (200 – 299 GDD50), again in early June (400+ GDD50), and again two weeks later. Spraying timing can also be determined by using pheromone traps (Make an application ten days after the first male moth is caught.) Prune and destroy infested canes. However, avoid pruning when moths are present.

Native Holly Leafminer (95)—We found the adult native holly leafminers on American holly on Long Island. They are ⅛ inch long black flies and can be found around the newly expanded leaves. Although the larvae only mine the leaves of American holly (Ilex opaca) the adults do feed on English holly (Ilex aquifolium) and Japanese holly (Ilex crenata) as well, causing leaf punctures to all of them. Examine young foliage of American holly for tiny green blisters. The parasites can not be relied upon as a control because they do not reduce the area mined and the resulting aesthetic damage. Place sticky traps on the terminals of holly to detect the adults. To manage large populations, treat in mid-May (192 – 298 GDD50).

Azalea whiteflies on underside of leaves. Inset: Close-up of an azalea whitefly.

Apple scab lesions are olive green, with uneven margins

Native holly leafminer damage. Inset: adult.

Branching Out—19

Privet Rust Mite (231)—This eriophyid mite was active at our scouting sites on Long Island and in central NY. These mites are white to yellow and spindle shaped with four short anterior legs. Even when viewed with a hand lens, they are so small that they appear as specks of dust or pollen. The host plants of this pest are the amur privet and the California privet and regal privet. The immature mites suck leaf juices and introduce toxins that cause leaves to cup downwards and turn olive green. Premature leaf drop and silvery stippling of foliage are also symptoms. Predaceous mites are the most effective natural enemies to these pests, but horticultural oil, neem oil or other registered pesticide can be used in the last 10 days of May through Mid-June (298 – 802 GDD50).

Rose Leafhopper (198)—Rose leafhopper nymphs are feeding on the underside of some rose leaves and damage is becoming apparent. These nymphs were white and look like tiny adult leafhoppers without wings. Leafhoppers feed by sucking the chlorophyll from leaves, resulting in minute white stippling of leaves (similar to mite damage but larger). Both the nymphs and adults cause damage. Control is usually not necessary unless a severe infestation is present.

Two-spotted Spider Mite (229)—This mite is active now in southern New York. The two-spotted spider mite is green or greenish yellow with two dark spots that can be seen through the pale bodies of these mites. This mite causes stippling of foliage and can be a serious pest of roses, flowering fruits, azalea, and several other shrubs. In addition, it may cause damage to maple, elm, redbud, ash, black locust, and poplar. Natural predators may greatly reduce populations. Heavily infested trees may need treatment with horticultural oil, insecticidal soap, neem oil or other registered pesticide. Treatments can be applied from late May through mid-June (363 – 618 GDD50).

White Prunicola Scale (188)—We found the eggs of this scale on our scouting trip to Orange County. The salmon colored crawlers should be active soon. Hosts include lilac, flowering cherries, privet, willow and catalpa. Predators and parasites are numerous but are not reliable. Treatments should be made to target the crawlers in mid-June through early July (707 – 1151 GDD50). Power wash or scrub off heavy infestations on the trunk with a brush.

Things to Look For in the Upcoming WeeksArborvitae Leafminer (14)—Brush the foliage of arborvitae to find the adult moths of this leafminer. The adults are 1⁄3 inch long and silvery gray. Feeding by the larvae of this pest turns the tips of shoots and the foliage brown. There are many effective larval parasites that suppress the populations so chemical control may not be necessary. If infestation is light, prune out infested tips. If control is needed, treat between 533 – 700 GDD50 for the moth stage. See Cornell Guidelines for more information.

Bagworms (80,81)—You will soon see spindle-shaped bags that are attached to twigs and foliage of cedar, arborvitae, juniper, and other conifers. This pest is not common in the northern parts of NY State but if you live in Southeast NY they can be of concern. Several parasitic insects are present in most bagworm populations, yet they are rarely an acceptable mean of control. In light infestations, hand pick and destroy bags. Sex pheromone traps help in reducing the bagworm populations. With heavy infestations registered pesticides can be applied in mid-June (600 – 900 GDD50). Thoroughly cover the foliage.

Bronze Birch Borer (128)—The adult bronze birch borers will soon be found crawling on the sunny sides of trees. The borers are greenish bronze in color and have blunt heads. The body is slender, pointed, and one fourth to half an inch long. The bronze birch borer creates D-shape holes in the bark. The first symptom of infestation is the yellowing and browning of foliage in the upper branches. As the boring increases, the trunk bleeds, the tree declines, and the foliage becomes more sparse. Treat in June (440 – 880 GDD50).

Lophodermium Needlecast (11)—Lophodermium seditiosum fruiting bodies should begin to produce infectious spores within the next few weeks. As the nature of this disease is to produce spores over a period of about four months, a simple schedule of treating once a month with a registered fungicide beginning in early July and continuing into early October has been found to be a fairly effective management strategy.

Mountain Ash Sawfly (56)—The larvae will soon begin feeding on the leaves of mountain ash. Control is usually not warranted. The larvae feed in groups, so small populations can easily be pruned out or squashed. If the infestation is severe, treat in early to mid-June (448 – 707 GDD50).

Oak Spider Mite (228)—This warm season mite will be active soon. It is dark reddish brown, similar to southern red mite. They can be found on the upper leaf surfaces of oak, chestnut, birch, beech, elm and hickory. If necessary treat with horticultural oil, insecticidal soap or other registered pesticide in late June through early July (802 – 1266 GDD50).

Oystershell Scale (177)—The crawlers will be active soon. This pest may be found on apple, lilac, ash, willow, p o p u l a r , maple, and dogwood in late May. If predators are not preventing

Rose leafhopper damage. Inset: Nymph

Lophodermium fruiting bodies

Close-up of white prunicola scale with some covers removed to expose the bright orange females © Dan Gilrein

There are many effective larval parasites

Oystershell scales closeup

20—Branching Out Dawn Dailey O'Brien and George W. Hudler, editors

damage to the host, treat with a registered pesticide in late May through mid-June (363 – 707 GDD50). Several sprays may be required. There is one generation per year.

Pine Tortoise Scale (41)—The crawlers will be becoming active. Treat salvageable infested trees with insecticidal soap, horticultural oil, or other registered pesticide in mid -to late June (618 – 1050 GDD50). In Christmas tree plantations cull those that can’t be restored to marketable quality immediately.

Southern Red Mite (229)—The southern red mite will be active soon. It is the most widespread, important, and destructive spider mite on broad-leaved evergreens and cause bronzing and stippling of foliage. Treatment can be applied from 618 – 802 GDD50.

PhenologyLong Island: Flowering—Beautybush, cotoneaster,

deutzia, doublefile viburnum, dove-tree, enkianthus, Kousa dogwood, Miss Kim lilac, ruby horsechestnut, weigela, ‘Winter King’ hawthorn

Orange County: Flowering—Beautybush, burning bush, enkianthus, Kousa dogwood, white fringetree

Tompkins County: Flowering—Beautybush, black locust, golden chain tree, horsechestnut, Miss Kim lilac. white fringe tree

Westcheser County: Flowering—Burning bush, enkianthus, Miss Kim lilac

As of May 26, 2015Growing Degree Days

Station GDD50

Albany ..............................447Binghamton ......................347Boston, MA ......................354Bridgeport, CT .................392Buffalo .............................362Central Park .....................629Farmingdale (5/25) ............380Hartford, CT .....................488

Station GDD50

Ithaca ................................316New Brunswick,NJ ...........511Riverhead (5/27) ................421Rochester ..........................412Syracuse ...........................395Watertown ........................261Westchester ......................405Worcester, MA .................348

Our Financial SupportersThis issue of Branching Out was made possible with the generous gifts from the following: Jon HickeyAlmstead Tree, Shrub & Lawn Care Co.Cayuga Landscape Co., Inc.Emerald Tree CareGary Mosca & SonLong Island Arboricultural AssociationNew York State Arborists-ISA ChapterProfessional Tree Surgeons SupplyCarmine SerpeWhitman Nurseries