Pesticide Education Program

Supplement to the

PENNSYLVANIA

PESTICIDEAPPLICATOR CERTIFICATIONCORE MANUAL

INTRODUCTION 1

IntroductIon

The U.S. Environmental Protection Agency produced a National Pesticide Applicator Certification Core Manual that states are en-couraged to use. Pennsylvania is now using this manual, but it has been renamed the Pennsylvania Pesticide Applicator Certification Core Manual. One of the major differences between this manual and the previous Pennsylvania core manual, the Pesticide Education Manual, is that the new manual does not contain chapters on insects, weeds, plant diseases, or vertebrates. However, these chapters contain important information for private applicators, and for commercial and public applicators in a few categories. Specialists at Penn State have reviewed and updated these chapters. This information was then combined into this supplement. Some ques-tions on the certification examinations will be taken from this material.

Chapter 1: Management of Insects and Related Pests ...3

Chapter 2: Weeds and Weed Control ..................... 13

Chapter 3: Plant Diseases and Plant Health ............. 35

Chapter 4: Vertebrate Pest Management ................. 49

Answers to Review Questions ............ 57

MANAGEMENT OF INSECTS AND RELATED PESTS 3 3

CHAPTER 1

In this chapter we will introduce you to the insect world. We will discuss the types of damage caused by insects and related pests and many of the methods used to manage them. Identification of a suspected insect pest is extremely important because only a very small percentage of the insects on Earth ever actually become pests. Many other insects are beneficial as pollinators of crops, producers of honey, or as predators or para-sites of pests. Identification is also critical to implementing a successful control program. For example, control recommendations on pesticide labels are often pest specific. A pest management program generally fails unless the pest is accurately identified. Scientific names are given to each spe-cies of plant and animal on Earth. Although many plants and animals also have com-mon names, the scientific naming system is universal, assigning an organism one name to be used regardless of where it is found.

ManageMent of Insects and related PestsCompiled by Steve Jacobs, Senior Extension Associate, Penn State Department of Entomology, and updated by Shelby Fleischer, Greg Hoover, Steve Jacobs, Greg Krawczyk, and John Tooker, Penn State Department of Entomology Extension Team

This naming system categorizes plants and animals based on their similarities; for ex-ample, animals with common characteristics are placed into large groups, then subdi-vided into smaller groups, and finally given a specific name. All insects and related animals such as mites, ticks, and spiders belong to a large group called Arthropoda. Members of this group are called arthropods. They have seg-mented bodies and segmented appendages, some of which are modified for feeding, and a hard exoskeleton (exterior skeleton), which provides support and a protective covering. On the basis of common char-acteristics, arthropods are separated into smaller groups called classes. The common classes of arthropods are Insecta (insects), Arachnida (spiders, ticks, mites), Malacos-traca (crabs, sow bugs), Chilopoda (centi-pedes), and Diplopoda (millipedes). Most arthropod pests are insects and arachnids.

4 CHAPTER 1

INSECTS

Insects bear unique external features and undergo developmental processes unlike other organisms in the animal kingdom. An understanding of these characteristics is important for identification and control of pest insects.

Physical Characteristics External characteristics of insect adults that set them apart from other animals are three distinct body regions (head, thorax, and abdomen) and three pairs of jointed legs.

HeadThe head contains one pair of antennae, two compound eyes, ocelli (simple eyes) if present, and mouthparts. Antennae vary in size and shape but contain many sensory receptors for smell, wind, and temperature. The compound eyes are made up of many small facets that permit insects to discern images. Ocelli, on the other hand, perceive

motion rather than actual images. The four general types of mouthparts found on insects are chewing, piercing-sucking, sponging, and siphoning. Chewing mouthparts have toothed mandibles that bite and tear food. Cockroaches, grasshoppers, ants, and beetles have chewing mouthparts. Piercing-sucking mouthparts have a long, slender tube that penetrates the plant or animal tissue to suck out fluids or blood; true bugs, aphids, mosquitoes, and sucking lice have this type. Sponging mouthparts have a tubular, tonguelike structure with a sponge tip to suck up liquids. This type of mouthpart is found on houseflies. Siphoning mouthparts are formed into a long tube for sucking nec-tar. Butterflies and moths have this type. An insect’s mouthparts determine how it feeds and what type of damage it causes.

ThoraxThe thorax consists of three segments with one pair of jointed legs per segment. If one pair of wings is present, they will be on the second segment. If two pairs of wings are present, they will be on segments two and three, named forewings and hind wings, respectively. The forewings are modified in different insect groups. Beetles have forewings that are hard and shell like; grasshoppers have forewings that are leathery. Forewings of true bugs are partly membranous. Wings of moths and butterflies are membranous but covered with scales. Most hind wings of insects are membranous, and if only one pair of wings is present, they are membranous.

AbdomenThe abdomen is also segmented. The diges-tive tract, the reproductive system, and other vital organs are found in the abdomen. The abdomen also houses the external genitalia. These external reproductive structures of insects are often highly specialized and com-plicated and important for identification.

Development and MetamorphosisThe series of events from egg to adult con-stitutes an insect life cycle. The life cycle varies in each insect species, but knowledge of the life cycle is essential for a control program to be successful. Because the vari-ous stages in an insect’s life cycle can look so different and appear at different times,

Diagram of an insect

Types of mouth parts

Eye

Eye

EyeEye

Head Thorax Abdomen

Antennae

Mandible Beak

SpongePiercing stylets

Chewing Siphoning

Piercing-sucking Sponging

Sheath

MANAGEMENT OF INSECTS AND RELATED PESTS 5 5

it can be quite easy to miss an infestation if you are not familiar with the developmental cycle of a pest. Also, not all stages in an insect’s life cycle may be pests. For example, only the larval stage of a particular insect may cause plant damage. If the insect has already matured to the adult stage, the dam-age may be over for the season and control efforts will not be needed. Frequently, differ-ent stages in an insect’s life cycle are more easily and effectively controlled than others. Eggs and pupae are typically less affected by insecticides than are the larvae and adults. And immature larvae are usually easier to control than older larvae. Certain stages of insects may be difficult to control because they “escape” the control procedures. The larvae of many boring insects, for example, are difficult to control with insecticides after they enter the plant tissue and are out of reach of the chemical. Knowledge of an insect’s life cycle can help you target your control efforts to the most susceptible stage. Most insect reproduction is sexual—that is, an egg cell from the female develops only after it is fertilized with a sperm cell from the male. The females of most insect species lay eggs. However, some insects also have spe-cial modes of reproduction. One example is

parthenogenesis, in which an insect develops from an unfertilized egg. The number of eggs produced by females varies from one egg to many thousands for some social insects. A newly hatched insect differs in size and often in form from the parents. The change that must take place before the young insect becomes an adult is called metamorphosis. The degree of change varies widely in different insects. In some cases the changes are slight and gradual; in others they are rather dramatic, resulting in a total change of appearance in the insect. These variations have led to the classification of metamorphosis. If the changes are slight and gradual, the young or nymphs resemble the adults and feed in the same habitat, and wing development is external, then meta-morphosis is termed simple or gradual (as on the graph below). Grasshoppers, cockroach-es, and aphids are examples of insects with this type of development. However, the majority of insect species have a pupal stage and undergo much more drastic alterations. Development is termed complete meta-morphosis when the insect goes from egg to larva to pupa to adult. Insects that undergo complete metamorphosis include butterflies, flies, bees, ants, beetles, and moths.

Gradual metamorphosis

Complete metamorphosis

Egg Nymphs Adult

Egg Larvae Pupa Adult

6 CHAPTER 1

INSECT RELATIVES

The arthropod classes closely related to insects are Arachnida, Crustacea, Chi-lopoda, and Diplopoda. Although animals in these closely related classes are often called insects, they are not insects. The four classes contain species that are detrimental to humans and the environment. We will cover some of the biology of each class and how to tell them apart.

ArachnidaAnimals in this class, called arachnids, include spiders, ticks, mites, scorpions, pseu-doscorpions, whipscorpions, sun spiders, and harvestmen (daddy longlegs). The physical characteristics of arachnids are four pairs of legs on adults, and two body segments called the cephalothorax and the abdomen. Arachnids do not have antennae. Except for certain mites, arachnids are carnivorous and terrestrial. The life cycles of the arachnids are variable and complex. Some ticks, for example, require three different hosts and up to three years to complete their life cycles. Many arachnids have poison glands that produce toxins used to kill prey. Bites and stings from the black widow spider, brown recluse spider, and some scorpions produce toxins that are harmful to humans. Mites are the most destructive arachnid pests of plants. Many species of mites attack a wide variety of hosts, often damaging the chlorophyll-producing tissues.

MalacostracaThis large class consists of approximately 50,000 species possessing a head, thorax, and abdomen. Crustaceans also possess mandibles, two pair of antennae, and five or more pairs of legs. Most crustaceans are aquatic. One common terrestrial species called the sow bug is usually found in damp areas such as under decaying wood or bales of hay. Sow bugs are not harmful but may become pests if present in large numbers.

ChilopodaCentipedes have a long multisegmented trunk and a head with a pair of moderately long antennae, a pair of mandibles, and two pairs of maxilla (additional jaws). The main characteristic of centipedes is that each seg-ment has one pair of legs. Centipedes usually hide during the daytime and are active at night. Their food consists of other arthropods, earthworms, and slugs. Centipedes produce a toxin to kill their prey, but it is seldom dangerous to humans.

Diplopoda The millipedes represent another group that has a body separated into a head and trunk. The head contains a single pair of short an-tennae, a pair of mandibles, and a single pair of fused maxilla. The main characteristic of millipedes is two pairs of legs per segment. Most millipedes are found in rotting logs, leaf litter, and under stems, where they feed mainly on decaying vegetation and fungi. When disturbed, they often roll into tight coils to gain protection with their hard exterior. Many have specialized glands to secrete noxious fluids, such as hydrogen cyanide, to repel predators. Millipedes do not pose a threat to humans.

Tick

Sow bug

Centipede

Millipede

MANAGEMENT OF INSECTS AND RELATED PESTS 7 7

DAMAGE CAUSED BY INSECTS AND RELATED PESTS

Insects, ticks, and mites damage plants, animals, and structures in different ways. The damage often provides clues as to the identity of the pest, as well as the fate of the host. For example, defoliation by insects in the spring is usually more detrimental to a plant than defoliation in late summer because the plant is preparing to drop its leaves anyway. Different types of pest dam-age can be classified as follows.

Plant Pests

DefoliatorsOne of the more obvious types of dam-age done to plants by insects is defoliation caused by the eating of leaf tissue. The most economically important group of defoliators is the caterpillars, or larvae of butterflies and moths. Examples include the gypsy moth, which feeds on trees, and the imported cab-bage worm, which feeds on cabbage leaves. Beetles are also important defoliators. Ex-amples include the Colorado potato beetle, Japanese beetle, and Mexican bean beetle.

Internal FeedersInternal feeders are larvae that feed and develop (even pupate) inside fruit, grain, or other plant parts. Examples of internal feed-ers are the cotton boll weevil, rice weevil, birch leaf miner, and codling moth. Inter-nal feeding insects often cause losses that are not easily detected until the damage is extensive.

Stalk or Stem BorersMany larval stages of insects bore into stalks or stems. This destroys tissues, weakens the stalk, and prevents adequate translocation of water and nutrients within the plant. Weakened plants may blow over or wilt as a result of the damage. Examples of boring insects include the European corn borer, squash vine borer, and dogwood borer.

Plant-Sucking PestsMany arthropods have mouthparts adapted to sucking juices from plants. Symptoms of plant damage caused by sucking pests such as aphids, leafhoppers, whiteflies, scales, plant bugs, and some mites include curling and stunting of leaves and stems, wilting caused by the blockage of water-conducting tissues, and dead areas caused by the injec-tion of toxins by the pest during feeding.

In addition to the direct feeding damage, an important economic effect of plant-sucking pests is the vectoring (transferring) of plant pathogens (disease-causing organ-isms). This is also discussed in Chapter 3. Aphids, whiteflies, mealybugs, and some other sucking insects excrete honeydew, which drips onto the lower parts of the plant. This sticky material makes an excel-lent substrate for a fungus that produces a black sooty mold. Sooty mold can be detrimental to the plant if the insect is not controlled.

CutwormsAs the name suggests, the cutworms sever plant stems at ground level. Cutworms are hard to see because they feed at night and remain underground during the day. These characteristics can make them difficult to control.

Subterranean FeedersNumerous insects cause damage by feeding on the roots of plants. They are often diffi-cult to identify because they cannot be seen without uprooting the plants. Root feeding can lead to dead spots in lawns, goose neck-ing in corn, or poor color and reduced vigor in plants. Examples of insects that feed on roots are white grubs, corn rootworm, black vine weevil, and many maggots of flies.

Animal PestsThe insects, ticks, and mites that attack hu-mans and animals have mouthparts similar to those of the plant feeders, but they feed on blood and vertebrate tissues rather than plant tissues. Mosquitoes, lice, and ticks are blood-sucking pests. Cattle grubs, the ox warble of cows, and the bot fly of horses are examples of internal feeding insects. Face flies, houseflies, and gnats are annoying and cause discomfort. Some pests are vectors of disease-causing organisms. These pests are able to introduce bacteria, viruses, or other parasites into animals as they feed. In the United States, mosquitoes carry encephali-tis, and ticks carry Rocky Mountain spotted fever and Lyme disease.

Aphid

Mosquito

8 CHAPTER 1

Structural PestsMany insects attack and destroy wood struc-tures. The most important wood-damaging pest is the subterranean termite. This insect can digest cellulose (a major constituent of wood) with the aid of a microorganism that

lives in its gut. Termite mandibles are very strong and can rapidly destroy wood. Many other structural pests such as powder post beetles and old house borers are internal feeders. Damage is caused by the larval stage of these insects.

MANAGING INSECTS AND INSECT RELATIVES

A few basic principles are necessary for a successful pest management program. Rarely discussed in textbooks is the need to visit fields or structures regularly and to be obser-vant as to what is occurring. Being a good observer is the first step in identifying the pest or pests involved in damaging a product or property. Once a pest is recognized, it is then necessary to learn about the biology of the pest, what kind of damage the pest can do, and what control tactics are available. The next step is to monitor the area in question and determine whether the popu-lation level warrants immediate suppressive action. The population level of the pest may be tied to an economic threshold. Action is often recommended when the pest level is high enough to reduce crop value by an amount greater than the cost of implement-ing the pest management response. The general tactics for managing pests include biological control, host-plant resistance, genetic control of the pest, cultural con-trol, physical and mechanical control, and chemical control. After evaluating all available tactics, a management system can be developed that best suits the situation.

Some of the tactics, such as variety selec-tion and certain cultural methods, must be considered at planting time or prior to the occurrence of the pest.

Alfalfa Weevil Integrated Pest Management (IPM) ProgramThe alfalfa weevil program illustrates many of the principles of insect pest management. The alfalfa weevil can overwinter as an adult or an egg. Some eggs are deposited in the fields in the fall and survive the winter. However, about 90 percent of the eggs are deposited in the spring, with most of them laid before mid-May. Larvae that hatch from these eggs move to the tips of the plants and feed on the leaves. This feeding results in reduction of both alfalfa yield and quality. The small, green, curved larvae, with dark brown to black heads, reach maturity in approximately three weeks (normally about June 1 in southern Pennsylvania). They pu-pate in small, round, loosely woven cocoons attached near ground level to plant debris, leaves, and stems. Estimates of alfalfa weevil development around the state can be viewed with the Pennsylvania PIPE (Pest Informa-tion Platform for Extension and Education), which is an online plant and pest phenology tool available at extension.psu.edu/pa-pipe. After the larvae pupate, no further dam-age occurs for the year because very little weevil activity occurs during the summer and fall months. Alfalfa weevil injury is almost entirely limited to the first cutting, with some possible damage to the regrowth of the second cutting. Alfalfa weevil damage is usually complete by mid-June. The new brood of adult weevils emerging at this time spends the summer in protected sites both in and outside the alfalfa fields.

Sampling for Alfalfa WeevilIn recent years, feeding by alfalfa weevil larvae has been negligible before the first week of May. Noticeable feeding injury to

Termite

Alfalfa weevil

Pupa

Eggs

Larva

Adult

MANAGEMENT OF INSECTS AND RELATED PESTS 9 9

the plant tips provides the signal to start monitoring alfalfa fields. The month of May is the crucial time for weevil control spray-ing, if needed. Resampling fields at weekly intervals in May is recommended. This is especially important if certain fields are prone to weevil damage or if field condi-tions are nearing a treatment threshold.

Basis for the Economic ThresholdMany factors must be considered when determining the economic threshold for alfalfa weevil.

• The number of pests present in a field. The sample used is the number of larvae (all sizes combined) on 30 stems. Re-search has shown that a 30-stem sample provides a reliable indication of the weevil larvae population in a properly monitored field. Crop losses from weevils are predicted on the amount of foliage one larva per sample of 30 stems will destroy in relation to the development of the crop. For example, on alfalfa 12 inches high, one larva per 30-stem sample will reduce the hay equivalent yield by 0.00159 ton per acre, or 3.18 pounds.

• Development of plants. This is the height of the plants when the fields are moni-tored. Small plants infested with weevils suffer greater losses than large plants infested with equal numbers of weevils.

• Value of the crop. The higher the value of the crop, the fewer weevil larvae that can be tolerated.

• Cost of control application. As the costs of control measures increase, greater dam-age from the pest can be allowed before a spray application is warranted.

Economic thresholds for alfalfa weevil are available in Penn State’s alfalfa weevil fact sheet: ento.psu.edu/extension/factsheets/alfalfa-weevil. It is doubtful that many fields in Pennsyl-vania will need spray protection before May 10. Early spray applications generally are very hazardous to certain parasites that feed on weevils, and for this reason early spraying should be avoided if possible. Insecticides that have long residual action are more likely to kill the weevil parasites than are short-residual insecticides. Therefore, in most situations, short-residual insecticides are suggested when chemical control is needed.

Whether to Spray Before HarvestSome of the more difficult decisions come

near harvest time for the first crop, so determining whether to spray before harvest is important. A crop that is in full bud probably should be harvested rather than sprayed. However, if harvesting is impossible for at least three days and the pest popula-tion is increasing or holding steady, then application of a short-residual insecticide will leave no residue on the hay at harvest. Previous sampling records can be very helpful at this time. This information indicates whether the weevil population is increasing, has reached a plateau, or is decreasing. A decreasing population does not need to be sprayed because the weevil season is over.

Whether to Spray After Harvest The stubble of all fields should be checked from four to six days after mowing. Those fields that were not sprayed or were sprayed fairly early in the season should be checked first. If the larval population is fairly high, regrowth of the second crop can be drasti-cally delayed. If weevil cocoons are present and the larval number is low, the weevil sea-son is practically over and little additional damage is likely to occur. An average of two or more larvae per crown after harvest indicates that a stubble spray will be profitable. Apply it as soon as the forage is removed from the field.

Apple Integrated Pest Management ProgramThe integrated pest management program on apples also illustrates the important principles involved in insect and mite pest management. With a complex of more than 20 important economic pests that are able to harm the quality and yield of the fruit, a vigilant scouting and monitoring program needs to be imple-mented to correctly assess the occurring and possible threats to the apple crop. The implementation of IPM on apples can result in the use of less pesticide,

PestEuropean red mite

PredatorLadybird beetle

10 CHAPTER 1

POTENTIAL PROBLEMS ASSOCIATED WITH INSECTICIDE USE

the more efficient use of time and orchard equipment, and the use of native beneficial organisms as a major part of the pest man-agement program. An excellent example of integrating available tools for IPM is the control of European red mites. The mite IPM pro-gram is based on simultaneous utilization of mite predators, selective pesticides, and the alternate middle row system of pesticide applications. The complex of naturally oc-curring predatory mites Typhlodromus pyri, Amblyseius fallacis, and Zetzellia mali and predatory lady beetle Stethorus punctum are fully capable of controlling the phytopha-gous mite populations, but at the same time those beneficial organisms are very sensitive to pesticides used to control other pests and diseases. Also, the use of highly effective acaricides to control mites is capable of negatively affecting the survival of natural enemies by direct toxicity as well as by creating a “food shortage” situation. There-

fore, this IPM strategy employs a technique where only selective pesticides that are not harmful to beneficials are applied and a very vigilant monitoring system is incorporated to support the decision if specific acaricides are needed to reduce the mite populations. If, based on economic thresholds, the neces-sity of treatment is established, then only the alternate rows of trees are treated with acaricides. This way the economic dam-age is prevented and at the same time the surviving mites are still present on the trees that were not completely sprayed to support the population of beneficial organisms. The incorporation of alternate row middle sprays, while effective for pest control/sup-pression, also encourages the immigration and reproduction of the mite predators. In addition to the advantages described above, an integrated apple pest management program can reduce the likelihood of pests developing resistance to pesticides.

Insecticides often have a significant role in pest management programs. Their use, how-ever, requires planning and care to avoid problems, particularly the development of resistant pest populations and the injury of nontarget species.

Pest ResistanceResistance is the ability of an insect or other arthropod to tolerate an insecticide that once controlled it. Resistance develops because intensive insecticide use kills the susceptible individuals in a population, leaving only the

Some individuals in a pest population have genetic traits that allow them to survive a pesticide application.

A proportion of the survivors’ offspring inherit the resistance traits. At the next spraying these resistant individuals will survive.

If pesticides are applied frequently, the pest population will soon consist mostly of resistant individuals.

susceptible individual

resistant individual

Illustrations courtesy of the Pesticide Education Program and iStockphoto.com

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