Corn rootworms  Northern and western  are native to North America. Populations of the northern corn rootworm, first recorded in 1824, were confined to the north central United States until the mid-1950's. During the 1960's, the range of this species expanded into Pennsylvania. Western corn rootworm was first recorded in 1868 in Kansas and, by the mid-1950's, had spread only to Nebraska and portions of Colorado, South Dakota, and Iowa. For reasons unknown, population distribution greatly expanded between 1955 and 1970. Not until 1980, however, was western corn rootworm first observed in Pennsylvania. Since then, it has spread throughout the state and is now the predominant rootworm species in western Pennsylvania. Corn rootworms have long been the major economic pests of corn in the United States. In Pennsylvania, corn rootworm damage has been sporadic. Over the past several years, however, the invasion of western corn rootworms and the expansion of northern corn rootworm populations in the state have greatly increased the potential for economic losses. The influx of western corn rootworm into Pennsylvania has necessitated development of a management guide that encompasses both rootworm species. The objective of this publication is to inform corn producers, field scouts, and county extension agents of the biology of both rootworm species, ways to identify the species and the damage they inflict, as well as scouting methods, economic injury levels, and control strategies.
Life Cycle of the Corn Rootworm
Figure 1 depicts the life cycle of the corn rootworm. Both species of corn rootworm complete one generation per growing season. Adult corn rootworms begin emerging between mid-July and mid-August, depending on weather conditions during their summer developmental period. Adult emergence continues for four to six weeks. Adults of western corn rootworm usually begin to emerge five to seven days before those of northern corn rootworm. After emergence, the eggs of adult females mature within about two weeks. Once a female begins laying, she deposits 75 percent of her eggs over a period of 30 to 35 days. A female rootworm may live as long as 80 days and deposit more than 1,000 eggs during her life. She deposits her eggs mainly during August and September.   Corn planting   April May June July August September               Adults present in field                 Egg deposition occurring         Larval hatch                   Larvae present in field                     Pupal stage     Both species of rootworm prefer to deposit their eggs in cornfields. Females deposit most eggs near the base of corn plants, within the top six inches of the soil surface. (Western corn rootworm females may deposit their eggs throughout the field.) Small holes and cracks in the soil give the females access to areas below the soil surface. Once corn rootworm eggs are deposited, they remain unhatched until spring. The eggs of both species must be exposed to a period of cold before larvae can hatch. This physiological requirement is known as diapause. Any larvae that hatch in the fall die along with adults from the cold winter temperatures. Larvae begin to hatch from overwintering eggs during June and feed on corn roots. Depending on spring temperatures, eggs may begin to hatch anytime from early to late June. Western corn rootworm larvae tend to hatch five to seven days before northern corn rootworm larvae. The larval stage lasts from four to six weeks, after which pupation occurs. Adults begin to emerge five to ten days after pupation and feed on corn silks. Northern corn rootworm adults can be found feeding on the flowers of a number of plants, but they deposit their eggs primarily in cornfields.
Life Stages
The adult is the only developmental form of northern and western corn rootworm that can be distinguished visually without the aid of a microscope (Figure 2). Adult northern corn rootworm beetles are only about ¼ inch long and are solid yellowish green (tan when newly emerged). Western corn rootworm beetles are about the same size and color, but they have three dark stripes on their wing covers. On some beetles the stripes overlap, making the wings appear dark brown or black. Adults are very active and fly rapidly if disturbed. The spherical, whitish or yellowish eggs are deposited in the soil and are almost impossible to see. Larvae of both species are white, measure about 1/8 to 1/2 inch long, and have brown heads, six small forelegs, and slightly wrinkled skin (Figure 3). Larvae also have a dark plate on the top side of the last abdominal or tail segment. The pupae are white, but otherwise similar in appearance to the adult.
Figure 2. Adult Western (left) and Northern (right) Corn Rootworm	Figure 3. Corn Rootworm Larva.
Distribution
In Pennsylvania, western corn rootworm is now predominates across the majority of the state. The northern corn rootworm out numbers the western in some of the cooler and more northern regions of the state. Relative proportions of each species vary from site to site and between years at a site.
Damage
Both rootworm species can cause damage in their larval and adult stages. Newly hatched larvae feed on root hairs and outer root tissues, but also tunnel into the soft root tissue. Larger larvae tunnel into roots and occasionally into the plant crown. Tunnel openings are visible on the roots, and root tips appear brown and chewed back. Removal of root tissues restricts the water and nutrient uptake of the corn plant. Soil moisture largely determines the extent of rootworm damage to corn plants. Under moist soil conditions, most corn plants can compensate for rootworm damage by rapidly growing new root tissue. As long as the plants do not blow over during immediately after the roots are pruned, they typically will not experience significant yield reductions. Dry conditions restrict the plants ability to compensate for root pruning. No-till fields with soil compaction problems may be stressed even more severely by rootworm damage, because the root system is restricted to the upper six inches of soil where rootworm numbers are highest and the soil in more likely to dry out. Severe root pruning of small plants (four to six leaves) can kill the plant. Larger, more vigorously growing plants typically produce new root growth faster than larvae can prune the roots. At high rootworm densities, root pruning may be severe enough to cause plant lodging and reduce yields. Lodging occurs during the vegetative stages of corn development, so lodged plants continue to grow, orienting themselves toward the sun. As a result of this growth habit, the plant eventually looks "goosenecked." By the time "goosenecking" is evident, root pruning is nearly complete. Because western corn rootworm larvae tend to hatch earlier in the season and feed more vigorously than northern corn rootworm larvae, they are more likely to cause severe damage to corn roots. Adult rootworms feed on corn silks by clipping them off, sometimes before pollination. If the corn silks are not clipped back inside the husk and at least 1 inch of silk is extended beyond the tip of the husk, the kernels can still be fertilized. When clipped, the silks continue to grow. Therefore, as long as the rate of silk growth exceeds that of silk clipping, adult feeding does not interfere with pollination. Severe silk clipping during pollen shed, however, results in barren or poorly filled ears. Poor pollination from silk clipping is more likely to occur when plants are under drought stress. Once the silks turn brown, severe clipping does not affect yield, since browning indicates that pollination is complete.

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European Corn Borer

Description of Damage

Identification

Life History

Weather conditions play an important role in governing the survival of ECB. Strong winds and beating rains during peak flight activity may dramatically reduce both egg laying and egg survival. In contrast, curling and uncurling of corn leaves during periods of drought can help dislodge the eggs from a leaf.

Under ideal conditions, egg hatch of first generation ECB takes place within three to seven days after the eggs are laid. The tiny caterpillars feed on leaves in the whorl causing a "shot- hole" appearance after the leaves have uncurled. Older caterpillars tunnel in leaf midribs, but eventually bore into the stalk where they will complete their development in about three to four weeks. Full grown caterpillars pupate inside the corn stalks. In Virginia, second generation moths emerge and begin laying eggs from late June to mid-July. This second generation is considered to be the most damaging to corn grown for grain despite the fact that heavy infestations of first generation ECB can cause extensive visual damage.

Damage to corn by first-generation caterpillars is primarily physiological. Specifically, yield loss results from interference with transport of nutrients and water to the stalk and leaves. The extent of nutrient and water loss depends on weather conditions, soil type, plant variety, plant maturity, and level of infestation. USDA researchers in Iowa have shown yield reductions of about 8 bushels per acre from low ECB infestations and about 22 bushels per acre from large infestations.

Second generation damage consists mainly of stalk breakage, ear drop, and ear feeding, and is more physical and potentially much more serious than first generation damage. In general, heavy infestations of second generation ECB can reduce yields by as much as 30 bushels per acre. Stalk rot diseases also tend to be more prevalent in areas infested by second generation ECB.

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Cabbage and Seedcorn Maggot

PLANTS ATTACKED

Cabbage maggots can be very destructive pests of early-season plantings of cole crops: cabbage, cauliflower, broccoli, and brussels sprouts. Additional hosts include beet, radish, turnip, and celery.

Seedcorn maggots are known to attack asparagus, cabbage, turnip, radish, onion, beet, spinach, potato, and sprouting corn seeds. Seedcorn maggots can also be very damaging to beans and peas and new plantings of alfalfa.

DESCRIPTION OF DAMAGE

Cabbage maggots feed on feeder roots and tunnel into the taproot producing visible brown streaks on root crops suchasradishandturnip. Lowerleaves of infested cabbage and cauliflower plants often turn yellow, with severe damage resulting in arrested plant growth. Secondary infections of blackleg and bacterial soft rot diseases typically accompany cabbage maggot infestation. Factors such as cool temperatures and wet conditions, which delay germination during spring plantings,cangreatlyincrease thedamage caused by both the cabbage and seedcorn maggots.

Seedcorn maggots feed on sprouting seeds of numerous field and garden crops, but unlike cabbage maggots, typically do not infest plantings beyond the early seedling stage. In corn, seedcorn maggots bore into the gerrninating seed, often killing the germ. Failure of seedlings to emerge is usually the first indication of a seedcorn maggot infestation.

IDENTIFICATION

The adult stage of the cabbage and seedcorn maggots is a small (about 1/4 inch long), dark-grey fly that is similar in appearance to the house fly. The legless larvae of both species are white, tapered maggots that reach a size of about 1/3 inch long when fully grown. Maggots of these species are virtually indistinguishable from one another in the field. The cabbage maggot, Delia radicum (L.), and the seed corn maggot, Delia platura (Meigen), are members of the family Anthomyiidae in the order Diptera.

Cabbage Maggot: adult, maggot, pupa

Seedcorn Maggot: adult, maggot, pupa

LIFE HISTORY

Cabbage and seedcorn maggot adults typically emerge in April and begin laying eggs. Female cabbage maggot flies actively seek out and lay eggs on the lower portions of stems of young host seedlings or in nearby cracks in the soil. Within a few days the eggs hatch and the tiny maggots burrow down to the roots and begin feeding. About three to four weeks later pupation occurs in the soil which is followed about a week later by the emergence of second generation adults. Several generations may occur as late as early July, but the first generation is the most destructive. Soil-borne pupae of the last generation serve as the overwintering stage. The life cycle of the seedcorn maggot is similar to that of the cabbage maggot; however, the seedcorn maggot prefers to lay eggs in freshly-tilled soil that is high in moisture and organic matter, and especially in soil where animal manure has been applied because it is highly attractive to female seedcorn maggot flies during egg laying. The eggs of the seedcorn maggot hatch within a few days and the maggots begin feeding on decaying organic matter or the germinating seeds of wild or crop plants. Seedcorn maggots are known to be highly attracted to odors produced by germinating seeds.

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WIREWORMS

Coleoptera: Family: Elaterlidae

GENERAL

The wireworm is a slender, hard-bodied “worm” or larva that is found when tilling the soil. It is present in most soil types year round. The larval color varies from yellowishbrown to orange (Figure 1). The adult wireworm is known as the click beetle (Figure 2), because of its habit of clicking or snapping its body into the air when placed on its back. It varies in color from tan to black and ranges in length from one-quarter inch to over one inch, with the most common pest species averaging about one-half inch. Various species of wireworms are distributed throughout North America and most of the world. While the different species have much in common, they can have quite varied life cycles.

 LIFE CYCLE

Most species overwinter in the soil in either the larval or adult stage; however, a few species may overwinter as eggs. The adults, which live for several months, emerge in May and June. The female click beetle soon seeks sites for egglaying. She burrows down into the soil and usually lays eggs singly on or near roots or grasses. Therefore, wireworm problems are normally associated with weedy (grassy) potato fields or fields that have recently been in sod. However, a few species are direct pests of certain crops and are attracted to these crops within, rather then to grasses. The eggs hatch two to four weeks, and the young larvae begin to search for food. The larvae may take from two to six years to reach full maturity and pupate. Because of this long life cycle, the wireworm can be quite a problem. 1 2 4 3 Usually, many stages and sizes of this insect can be found in the soil at the same time.

DAMAGE

Wireworms are destructive to a wide range of plants but can be especially severe on corn and potatoes. Estimated losses to farmers, because of these insects, reach several million dollars annually. The wireworm will feed on the seeds, roots and stems of their food plants. With potatoes, wireworms may attack the seed pieces, causing a poor stand. Once formed, the roots may also be attacked, resulting in plants with poor vigor and reduced yield. Finally, the potato tubers may be attacked directly (Figure 3). If damaged in early stages of tuber growth, the result may be a deformed tuber. If the attack occurs later, small holes (Figure 4) or tunnels will result, lowering the quality of the potato and opening the tuber to bacteria, other insects or fungal infections, such as fusarium.

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Cereal Leaf Beetle

Authors: D. Ames Herbert, Jr., Virginia Polytechnic Institute and State University and John W. VanDuyn, North Carolina State University

Cereal leaf beetle, a native to Europe and Asia, was first detected in Michigan in 1962. Since that time it has spread throughout most of the mid-western and eastern United States and has become a significant pest of Virginia and North Carolina small grains. This insect can become very numerous in small grain fields and the larvae are capable of reducing grain yield by eating the green leaf tissue.

Description

Adult beetles are about 3/16 inch long and have metallic looking, bluish-black heads and wing covers. The legs and front segment of the thorax are rust-red.

Eggs are elliptical, about 1/32 of an inch long, and colored yellow to burnt orangish yellow. Most often the eggs are laid singly or end-to-end in short chains on the upper leaf surface between, and aligned with, the leaf mid vein.

Larvae are slug-like, have orange yellow bodies with heads and legs that are brownish-black.

However, body coloration is usually obscured by a black globule of mucus and fecal matter held on the body, giving them a shiny black, wet appearance.

Adults:

• Adults overwinter in fallen leaves, ground litter, or other debris, within wooded areas, or other protected sites in the vicinity of last seasons grain fields.
• In the spring, they lay eggs in small grain fields.

Eggs:

• Egg laying occurs during late-March through mid-April with adults preferring late-planted and thinly sown fields.
• Eggs hatch in about five days.

Larvae:

• Larvae develop in 10 -12 days.
• Peak larval populations occur in mid-April to early-May.
• Small larvae eat a very small amount, but when full grown have a voracious appetite.
• Upon reaching full size, they dig into the ground and pupate.
• After a short period in the soil, a new summer generation of adult beetles emerges in late-May and June.
• New beetles move from small grain fields and feed on grass plants, including corn in fields adjacent to the small grain fields.
• Adult feeding on corn appears like many line-etchings on the leaf blades. Damage is cosmetic rather than yield reducing.
• Adults do not lay eggs in corn.
• They remain inactive through most of the summer.
• In the fall, beetles move to overwinter ing sites.
• There is only one generation per year.

Although adults will feed on young small grain plants, their feeding does not affect the plants performance. Larvae eat long strips of green tissue from between leaf veins and may skeletonize entire leaves, leaving only the transparent lower leaf surface tissue.

Damage to fields:

Severely defoliated fields can take on a white "frosted" cast when lots of green tissue is lost on the upper leaves.

Yield reduction:

• Leaf feeding reduces the plant's ability to make its food and limits reproductive growth, particularly if the upper leaves are destroyed.
• Yield reductions of 10% to 20% are typical in infested commercial fields.
• Yield reductions of 45% have been observed when defoliation was near 100% and the damage occurred early in the heading period.
• Damage late in the head-fill period does not have a great impact.

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The sunflower moth,

 Homoeosoma electellum,

(Lepidoptera: Pyralidae)

Identification   

Adult sunflower moths are grayish, 8.0 – 12.0 mm (3/8 – 5/8 inches) long, and rest with the wings clasped tightly to the body, giving the moth a slender cigar shape. Eggs are difficult to observe in the field because they are normally laid at the very base of florets within the flower disk. Newly hatched larvae are pale yellowish but soon darken to shades of brown or purple with longitudinal white stripes. Tangled mats of webbing on the faces of flowers are indicative of feeding by later instar larvae.

Life History and Behavior

The sunflower moth is a migratory pest that breeds year-round in northern Mexico and moves northward with successive generations every year. The moths’ survival rate in the large heads of cultivated sunflowers is much higher than in the wild flowers of composite weeds that are its natural host plants where it is subject to much higher rates of parasitism. Conditions for population build-up to the south, combined with prevailing summer wind patterns, are likely the most important factors determining the number of moths arriving in Kansas and the localities affected in particular years. Under warm conditions, the moths can complete a generation every 30 days, so several overlapping generations can follow the initial migration. The adult moths are primarily nocturnal and descend from the air currents when they smell a field of flowers in bloom. Flowers in the early stages of bloom are favored for oviposition and females lay their eggs at the base of the florets. The moths feed on sunflower nectar and the pollen serves as an ovipositional stimulus

Early instar larvae feed on pollen and florets and may hollow out individual seeds. Later instars bore into the head consuming receptacle tissue and damaging many seeds. Although a portion of larvae pupate within the heads, the majority of mature larvae descend to the ground on silken threads to pupate in crevices or under leaf litter, or in the case of diapausing larvae, to seek an overwintering site 2-3 inches below ground. Although temperature models have suggested the sunflower moth could potentially overwinter as far north as the Kansas-Nebraska border, our observations suggest that conditions are not suitable for timely induction of larval diapause in Kansas. Thus, late-maturing larvae typically emerge ‘suicidally’ as adult moths in October, rather than entering winter dormancy. Thus most economically damaging populations are derived from the initial spring migration, although local second generation moths may sometimes infest later-planted fields.

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Asparagus Beetles There are two species of beetles that attack and cause economic damage to asparagus in New York. They are the common asparagus beetle, Crioceris asparagi (Linnaeus), and the spotted asparagus beetle, Crioceris duodecimpunctata (Linnaeus). The common asparagus beetle is the more widespread of the two species.

Common Asparagus Beetle Common Asparagus Beetle Adult ©2002. The Bug Network, Image Courtesy of: Clemson University - USDA Cooperative Extension Slide Series Common Asparagus Beetle Lavae ©2002. The Bug Network, Image Courtesy of: Clemson University - USDA Cooperative Extension Slide Series Injury: Both the larvae and the adults of the common asparagus beetle damage the asparagus plants. The overwintered adults emerge and begin to feed on the tender growing tips of newly sprouted asparagus. They eat out holes and cause a brownish discoloration of the tissue. The grubs will feed on the tender young tips and on foliage. The plant growth is seriously reduced and proper root development prevented causing a decrease in the size and quality of the crop. Description: The common asparagus beetle is 1/4 inch in length, has a bluish black head, legs and antennae tinged with green, reddish thorax and the wing covers are marked by yellowish patches and reddish borders. The larva or grub of this beetle is dark gray to olive green with black legs and head. Life History: Adult beetles overwinter in sheltered places such as piles of rubbish and heaps of old asparagus tops. They emerge from their shelter when the new shoots come up and oval, and deposited either singly or in rows of two to eight. Later in the season the eggs are laid on leaves and flower stems. The eggs hatch in 3 to 8 days and the grubs begin feeding on the tender tips. When the grubs mature, they drop to the ground and construct a small earthen cell where they transform into pale yellowish pupae. The adult beetles emerge from the pupae. There may be two or more generations a year depending on the climate.

Spotted Asparagus Beetle Spotted Asparagus Beetle Adult ©2003. Cornell University Image Courtesy of: David Smith - Cornell University Department of Entomology Injury: This beetle is most injurious in the early season when the adults attack the growing tips and sometimes eat the buds of newly sprouted asparagus. The beetles also feed on foliage eating out irregular areas. The larvae cause little damage because they feed inside the berries. Description: The spotted asparagus beetle is slightly larger and more robust than the common asparagus beetle. The adults are reddish-orange in color with black antennae, eyes, and underside of thorax. Each wing cover has six distinct black spots. Life History: The adult beetles overwinter in piles of debris. They leave their winter quarters about one week later than the common asparagus beetles and begin to feed on the tender young shoots. They do not deposit eggs until the plant begins to blossom, about three weeks after they’ve emerged. The egg is deposited singly on plants, usually those bearing fruit. The egg is 1/25 inch in length, olive brown, and attached to the leaf by one side. The grubs hatch in 7 to 12 days and are yellowish-orange in color with a black head and legs. The larva finds a berry and enters it at the blossom end. Inside the berry it feeds on the seeds and it may attack 3 or 4 berries before it is mature. When fully grown, it drops to the ground by a silken thread and spins a cocoon just under the soil surface. In New York State a second brood usually occurs in July.

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Bean Leaf Beetle

Description:

Adult: Varies in color and markings; typically reddish brown with black spots on back and a black band near outer wing margins, up to 1/4 inch long. Larva: Slender white grub.

Beans, peas, cowpeas, soybeans.

Damage:

Eats regular-shaped holes in leaves; larvae bore into roots.

Distribution:

In all eastern states. Damage usually restricted to small areas.

Lifecycle:

Bean Leaf Beetles overwinter as adults in leaf litter or weeds in a range of habitats, including forest, pasture, or fallow acreage. They become active as temperatures warm in spring and migrate to legumes, such as alfalfa, peas, and beans where they feed and mate. Eggs are laid in the soil around plants and hatch within one to three weeks. The larvae feed on plant roots until pupation. After emerging from the ground the beetles feed on bean leaves and pods. There are normally two generations annually.

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Cabbage Looper

Trichoplusia ni
Lepidoptera: Noctuidae

Cabbage looper larvae eat large, irregular holes in the outer leaves of cabbage plants, sometimes eating into the heads of cabbages. Heavy infestations often result in skeletonized plants, as all but the leaf veins are usually eaten. Cabbage loopers can be responsible for reduced yields, heads which fail to form, and the contamination of the edible portions of the plants.

Description:

Cabbage looper larvae are light green and 40 mm (1 1/2 inch) long when mature. Older larvae have thin white lines running the length of each side. Loopers get their name from their peculiar walking behavior. They have three pairs of slender legs at the front of their body and three pairs of stout prolegs on the last 1/3 of the abdomen and no appendages in between. They move by gripping with the front legs and dragging the back legs forwards while arching the back. They then grip with the rear prolegs and push forward to straighten the "loop." The cabbage looper moths are nocturnal and are rarely seen during daylight hours. The moths are grayish brown with a wingspan of 40 mm (1 1/2 inch). The front wings are mottled brown with a small silver figure-8-shaped spot near the center, while the second wing pair is uniformly brown.

Life Cycle:

Cabbage loopers overwinter as pupae attached to host plants and other nearby objects. The adults emerge in the spring and lay several hundred eggs singly on the upper surfaces of host plant leaves. Larval development may be completed in two weeks if weather is favorable, and the cabbage looper can have three or more generations per year in the northern United States.

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Spider Mites

Spider mites are not insects but are more closely related to spiders. These arachnids have four pairs of legs, no antennae and a single, oval body region. Most spider mites have the ability to produce a fine silk webbing. Spider mites are very tiny, being less than 1/50 inch (0.4mm) long when adults.

 

Southern Red Mite Female, Male, Larva

Many species of spider mites can be found in Ohio landscapes. The twospotted spider mite, Tetranychus urticae (Koch), and spruce spider mite, Oligonychus ununguis (Jacobi), are the most common pests. Other species with fewer host plants include: European red mite, Panonychus ulmi (Koch), found on apple trees; honeylocust spider mite, Platytetranychus multidigitali (Ewing); southern red mite, Oligonychus ilicis (McGregor), on a variety of plants; boxwood spider mite, Eurytetranychus buxi (Garman); and the oak mite, Oligonychus bicolor (Banks).

Types of Damage

Spider mites have tiny mouthparts modified for piercing individual plant cells and removing the contents. This results in tiny yellow or white speckles. When many of these feeding spots occur near each other, the foliage takes on a yellow or bronzed cast. Once the foliage of a plant becomes bronzed, it often drops prematurely.

Heavily infested plants may be discolored, stunted or even killed. Web producing spider mites may coat the foliage with the fine silk which collects dust and looks dirty.

Life Cycles and Habits

Spider mite species seem to be warm weather or cool weather active pests. The twospotted, European red, honeylocust, and oak spider mites do best in dry, hot summer weather. The spruce and southern red spider mites do best in cool spring and fall weather.

All spider mites go through the same stages of development. Adult females usually lay eggs on their host plants. The eggs hatch in days to weeks into the first stage, called a larva. Larvae are round bodied and have only three pairs of legs. The larvae feed for a few days, seek a sheltered spot to rest and then molt into the first nymphal stage. The first nymph now has four pairs of legs. The first nymphs feed a few days, rest and molt into the second nymph. The second nymphs feed, rest and molt into the adult stage. The males are usually the size of the second nymph and have pointed abdomens. The females have rounded abdomens and are the largest mites present.

Most spider mites spend the winter in the egg stage but the twospotted spider mite overwinters as adult females resting in protected places.

Twospotted Spider Mite

The twospotted spider mite is an example of a 'warm season' mite. This pest has been reported from over 180 host plants including field crops, ornamental plants, house plants and weeds.

The females overwinter in the soil or on host plants. The females become active in April and May when they seek out the undersides of leaves on suitable hosts. Each female may lay over 100 eggs. A single generation may require as much as 20 to as few as five days, depending on the temperature. These mites prefer hot, dry weather and often do not reach damaging populations in cool, rainy periods.

In the summer, the adults and nymphs are white with two greenish spots. However, overwintering females usually turn reddish-orange and can be mistaken for other mite species.

Spruce Spider Mite

The spruce spider mite is a common 'cool season' mite. This pest can be found on all types of conifers from spruces and pines to junipers and arborvitae.

This mite spends the winter in the egg stage attached to host plants. The eggs hatch in March to April and the mites can complete development in 3 to 4 weeks. If summer temperatures are constantly over 90 F, this mite becomes dormant and lays resting eggs. These eggs and adults resume activity in the fall when cooler temperatures return.

Conifers often react slowly to the feeding of this mite. Yellowing and bronzing of the needles may not become apparent until the heat of the summer, even though the damage may have occurred the previous fall and spring.

Control Strategies

Early detection of spider mites, before damage is noticed, is important. The tiny spider mites can be detected by taking a piece of white paper or cardboard and striking some plant foliage on it. The mites can be seen walking slowly on the paper. If 10 or more mites per sample are common, controls may be needed.

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Plant-Feeding Mites

Around 7,000 species of plant-feeding mites are known worldwide, and about half of these are members of the superfamily Eriophyoidea (gall, bud, and rust mites). The other half are distributed within the superfamilies Tetranychoidea (spider, flat, and peacock mites), Tarsonemoidea (broad and cyclamen mites), and the lesser known bulb mites of the family Acaridae (Astigmata). In the United States, these groups include about 2,000 species. However, recent studies indicate that hundreds of species within the country, have yet to be discovered and described.

Plant-feeding mites play important roles as agricultural pests of timber, fruits, vegetables, forage crops, ornamentals, and stored grains. In many instances, lack of information about the correct identity of mites, as well as our lack of adequate knowledge regarding their biology and ecology, have hampered our ability to effectively combat these mite pests.

Their small size and cryptic appearance make mites difficult to detect and thus, infestations are often overlooked. Once established in a new area, certain biological characteristics allow rapid escalation to pest status. These include high egg production, various modes of reproduction (parthenogenesis, paedogenesis, and sexual), short life cycles, a myriad of dispersal techniques, and adaptability to diverse ecological conditions. These traits combined with an exponential increase in world trade have set the stage for potentially devastating situations that may threaten the sustainability of the world's agroecosystems.

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Stink Bugs

Authors: Eric R. Day, Director, Insect Identification Laboratory and Tom Kuhar; Assistant Professor, Department of Entomology; Virginia Tech

Range and Plants Attacked

Description of Damage

Identification

Life History

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Cucumber Beetles

Coleoptera: Chrysomelidae

NOMENCLATURE: The name cucumber beetle refers to two species: The Striped Cucumber Beetle,Acalymma vittatum (Fabricius) and the Spotted Cucumber Beetle, Diabrotica undecimpunctata howardi Barber.

PLANTS ATTACKED: Cucumber, cantaloupe, winter squash, pumpkin, gourd, summer squash, and watermelon, as well as many other species of cucurbits. Cucumber beetles may also feed on beans, corn, peanuts, potatoes, and other crops.

DESCRIPTION OF DAMAGE: Cucumber beetles are important pests of cucurbits. They cause four types of damage: seedling destruction, flower and foliage damage, root feeding, and transmission of bacterial wilt disease. Damage from cucumber beetles starts in the spring with feeding by adults on the seedling stage of the cucurbits. The beetles feed on newly emerged cotyledons and stems, and they have been reported to go below ground level and feed on plants as they emerge. Adults lay eggs in the soil near the seedlings and larvae soon hatch and begin feeding on roots of the cucurbits. Larvae chew holes and tunnel into the roots. Damage by the larvae, except under dry conditions, is usually considered minor. The first generation of adults emerges in late June and early July to feed on the foliage and flowers. Feeding damage by cucumber beetles to foliage is usually very minor, but severe feeding on flowers can result in poor fruit set. The second generation emerges in September and October.

Probably the most serious damage by cucumber beetles is from transmission of bacterial wilt caused by Erwinia tracheiphila. Bacterial wilt can kill many plants in a field and seriously reduce the yield. The striped cucumber beetle and the spotted cucumber beetle have very similar life cycles and both can carry the bacteria, but both are not equally important pests on cucurbits. The spotted cucumber beetle, also known as the southern corn rootworm, is a general feeder and is a pest on other crops, peanuts and corn in particular. The spotted cucumber beetle, however, is not considered as serious a problem as the striped cucumber beetle. The striped cucumber beetle has a more specific host range and feeds almost exclusively on cucurbits in the adult stage. The larvae are dependent on cucurbits for development; they cannot live on any other host plant. Both beetles should be monitored where cucurbits are grown.

DISTRIBUTION: Cucumber beetles are native insects and occur throughout the United States from Canada to Mexico. They are most abundant and destructive in the southern range and are usually not a problem in sandy soil. Cucumber beetles are widely distributed throughout New York.

DISEASE TRANSMISSION: Cucumber beetles transmit bacterial wilt of cucurbits (caused by Erwinia tracheiphila). Wilting usually starts with a single leaf and spreads to the entire plant, killing it. A stringy, viscous, white bacterial ooze forming a 'string' between cut ends of an affected stem is considered diagnostic for the disease in the field. Bacterial wilt of cucurbits is a serious disease of cucumber and muskmelon, and to a lesser extent, pumpkin and squash. The impact of disease transmission during the growing season is probably the most important aspect of the cucumber beetle's biology.

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DESCRIPTION OF THE PESTS

Darkling beetle adults range from 0.12 to 0.25 inch (3-6 mm) long and are about half as wide. They are dirty black to rusty brown in color, but this may be obscured by dust or a thin layer of soil. Larvae are very similar to wireworms in appearance.

DAMAGE

Beetle adults girdle or cut off seedlings at or below the soil surface, and are mostly active at night. After plants reach a height of 4 to 6 inches, darkling beetles are usually not a problem. Darkling beetles sometimes invade cotton from grain fields, weedy areas, or from adjacent alfalfa.

MANAGEMENT

Watch for darkling beetle injury by walking the field during the seedling stage. Pay special attention to field edges and any low or weedy areas.

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Pickleworm

Description:

Yellowish-white, brownish head; with numerous dark spots across segments when young. Older larvae are greenish. Up to 3/4 inch long.

Common host plant(s):

Cucumber, squash, pumpkin, muskmelon, cantaloupe and squash.

Damage:

Feeds on flowers and leaf buds. Tunnels flowers, terminal buds, vines and fruits.

Distribution:

Southeastern part of country as far north as Connecticut, Illinois, Iowa, and Kansas. Winters in southern Florida and Texas; spreads northward late in season.

Lifecycle:

Pickleworms overwinter in warm climates, such as Florida, and migrate north as temperatures rise. Females begin to deposit eggs in midsummer on hairy cucurbit surfaces. Within about three days small pickleworms hatch and begin feeding for a period of two week. Larvae may feed on flowers, vines, and fruit, but their preference is for developing leaf or flower buds. Pupation occurs in cocoons formed inside rolled leaves. Moths emerge in approximately a week.

Cultural Control:

Plant early; very early spring plantings are seldom damaged. Destroy vines, unused fruits, adjoining weeds and trash as soon as crop is harvested. Spading or plowing in early fall will bury pupae. Stems infested with pickleworms can be slit and the borers removed; heap dirt over the injured stem to encourage rooting.

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Squash Bug

The squash bug is one of the most common and troublesome pests attacking squash and pumpkin plants. Both nymphs and adults suck sap from the leaves and stems, apparently at the same time injecting a toxic substance into the plant causing a wilting known as Anasa wilt of cucurbits. This closely resembles bacterial wilt, a true disease. After wilting, vines and leaves turn black and crisp, and become brittle. Small plants are killed entirely, while larger plants have several runners affected. Squash bugs are often found in large populations, congregated in dense clusters on vines and unripe fruits. Sometimes no fruits are formed.

Identification

Adult squash bugs are rather large, about 5/8 inch long and approximately 1/3 as wide. Adults are winged, brownish black, sometimes mottled with gray or light brown, flat-backed, and give off a disagreeable odor when crushed. Young, called nymphs, are whitish to greenish-gray, with black legs. Bugs vary in size from tiny, spider-like individuals when first hatched, to maturing nymphs, which are nearly as large as adults. Young nymphs have red legs and antennae with a green abdomen. A few hours later, red parts become black. Late instars are of a dark, greenish-gray color. Eggs are yellowishbrown to brick red laid in groups or clusters.

Life Cycle and Habits

Unmated adult squash bugs overwinter in the shelter of dead leaves, vines, boards or buildings and fly to cucurbits when vines start to grow. Following feeding and mating, egg laying soon begins. Masses of eggs, each containing about a dozen or more, are usually deposited on the undersides of leaves in angles formed by the veins. Egg laying by the overwintering females continues until midsummer. Eggs hatch in about 10 days or more, and the nymphs pass through 5 instars requiring 4-6 weeks to reach adulthood. Only one generation develops each year and new adults do not mate until the following spring. Squash bugs are secretive in habit. Both adults and nymphs are found clustered near the plant crown, beneath damaged leaves, under clods or in any protective groundcover. They all scamper quickly for cover when disturbed. Because of the protracted egg laying period, all life stages occur throughout the summer months.

Control Measures

Early detection of adult squash bugs is very important since they are difficult to kill and can cause considerable damage.

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Tobacco Budworm

(Order: Lepidoptera, Family: Noctuidae, Heliothis virescens (Fabricius))

Description:

Adult: Adults are medium-sized moths with wingspans of 28-35 mm. Adults are variable in color, but the front wings are usually yellowish-brown and are crossed transversely by three dark bands. The hind wings are creamy white with a broad dark band near the wing margins, but the margin of the hind wing is creamy white.

Immature stages: Eggs are pale green when first deposited, turn yellowish, and then darken with age. Eggs are shaped like a somewhat flattened sphere with ridges (18-25) radiating from the top-center. Larvae range in size from 1.5 mm at hatching to 25-36 mm at maturity. The head tends to be yellowish-brown, and the body color may be brown, green, pink, or sometimes yellow or maroon. The larvae closely resemble corn earworm larvae. A key characteristic that will separate corn earworm and tobacco budworm larvae from most other species encountered in vegetables is the presence of black microscopic spines on the cuticle. The pupal stage occurs in the soil. Pupae are 18 mm in length and mahogany-brown.

Biology:

Life cycle: Eggs are deposited individually on leaf tissue and hatch in 3-4 days. Females can lay about 300-500 eggs with as many as 1500 over their lifetime. Larvae can feed and develop on foliage, but preferentially feed on buds. Larvae usually develop through 5-7 instars in 17-18 days at 25°C. Larvae fall to the ground and burrow into the soil to pupate. The pupal stage lasts about 13 days in the summer and serves as the overwintering stage in the late fall.

Seasonal distribution: Tobacco budworm can attack vegetable crops throughout most of the production season, but it has rarely been a problem in tomato and pepper.

Damage to Crop:

Tobacco budworm damage is caused only by the larvae. Larvae have chewing mouthparts and remove plant tissue. Although larvae can feed and develop on leaf tissue, the preferred feeding site in most crops is the buds or fruiting structures.

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Whiteflies