Garden Pests
APHIDS
Aphids are very common garden pests. They are small, soft-bodied, pear-shaped insects, generally less than 1/8" long. Most are green or black but they can also be found in a variety of other colors as well. A characteristic common to all aphids is the presence of cornicles, or tubes, on the back ends of their bodies. These cornicles secrete substances that help protect the aphids from predators. Over winter, aphids exist as eggs on perennial plants and hatch in the spring.
The insects cause injury to plants by sucking the sap and juices from the soft, new growth. This damages the host plant's ability to properly process food and causes the plant to lose vigor, wilt, distort or show spots. Aphids also can infect healthy plants with viral diseases they have picked up from unhealthy plants.
They often live in large clusters or colonies and are found together with ants. The ants feed on the honeydew produced by the aphids and protect the aphids in return, often keeping their eggs through the winter in their nests. In the spring, the ants transport the aphids to host plants and then protect them from enemies.
Natural enemies play an important part in controlling aphids. Lady beetles, lacewings, damsel bugs, flower fly maggots, certain parasitic wasps, birds, and fungal diseases all attack aphids.
Prune off and destroy heavily infested plant parts.
Most aphids can be controlled with the use of insecticidal soaps. Insecticidal soaps are non-toxic and safe to use in backyards.
Aphids are attracted to yellow. Try placing a sticky yellow-color trap nearby to lure the aphids away from plants.
Avoid the use of high-nitrogen fertilizers. Aphids thrive when the nitrogen in the plant sap is high.
CUCUMBER BEETLE
A common pest of the home garden, cucumber beetles are either striped (Acalymma vittatum) or spotted (Diabrotica undecimpunctata howardi). These native insects are found across the United States from Canada to Mexico, but are most troublesome in the south and where soils are heavy. Both species feed primarily on the leaves, flowers, and fruits of cucurbits (cucumbers, squash, pumpkins, and melons). Alternate plant hosts include beans, corn, peanuts, and potatoes.
Adult beetles (1/4 inch long) are yellowish-green in color with dark heads, legs, and antennae. They have distinct black spots or lengthwise stripes on their wings. During the growing season, they are found feeding on seedlings, foliage, pollen and flowers, causing greatly reduced yields and sometimes plant loss. The slender, white larvae (up to 1/3 inch long), have brown ends and injure plants by feeding on roots and underground stems. Heavy larvae populations can reduce plant vigor and damage melon rinds.
Adult and larval stages of the cucumber beetle transmit several plant diseases, including bacterial wilt and cucumber mosaic virus in cucurbits.
Adult beetles overwinter in plant debris and garden trash. Females leave their winter sites in early spring and deposit up to 800 orange-yellow eggs in the soil near the base of plants. In about 10 days hatching occurs and the larvae feed for three or more weeks before pupating. First generation adults emerge 10 days later. A complete life cycle requires 6-9 weeks. Up to four generations can be produced in a single growing season.
To control select resistant varieties whenever possible. Inspect plants frequently for beetles and handpick any that are discovered. Floating row covers are extremely effective when placed on seedlings and left in place until plants are old enough to tolerate beetle damage. Commercially available beneficial insects, such as ladybugs, lacewing and the spined soldier bug, will feed on pest eggs. Beneficial nematodes work well to control immature stages in the soil. If pest levels become intolerable, spot treat with botanical insecticides. Remove garden trash and other debris shortly after harvest to reduce overwintering sites.
Tip: Secure row cover edges to ensure that the beetles do not find a place of entry.
FLEA BEETLES
One of the earliest garden visitors are flea beetles. Aptly named, they are among the smallest of beetles and readily jump, flea-like, when disturbed. As a result, the insects sometimes elude the gardener but the damage they cause to plants is distinctive. Flea beetles chew small pits into leaves, giving plants the appearance that they may have been blasted with fine shot.
Flea beetles are most damaging to plants that are in seedling stages or struggling to become established after transplanting. In extreme cases plants may be so badly chewed that they are killed or greatly retarded.
However, established plants that are actively putting on new growth are little affected by flea beetles, fully compensating for the injury they produce. Thus the key to avoiding problems can be to provide cultural conditions that allow for vigorous plant growth and rapid establishment in the garden.
Trap cropping can sometimes be used to allow seedling crops to get over the hump and past the point where flea beetles can seriously affect the crop. For example, radish and daikon are extremely favored by the cabbage flea beetle. Yet these fast growing plants are vigorous enough to well tolerate the insect - although there may be many holes in the leaves. By planting these near a more susceptible crop, such as seedling mustard or broccoli, a large number of the flea beetles will be diverted to the radish, to draw pests away from the main crop..
Note: Flea beetles transmit viral and bacterial diseases.
Adults overwinter in the soil or garden debris and become active in the spring, feeding on host plants as new growth appears. Tiny white eggs are laid on or in soil cracks around the base of plants. These hatch in about one week, and the slender white larvae feed on plant roots for approximately 2-3 weeks. Pupae usually remain in the soil for 7-9 days until adults emerge and the cycle is completed. There are one to four generations per year, depending on species and climate.
To control remove garden trash and plow or roto-till under weeds to reduce overwintering sites. Floating row covers are extremely effective when placed on seedlings and left in place until plants are old enough to tolerate beetle damage. Place yellow sticky traps throughout garden rows every 15 to 30 feet to capture adults. Beneficial nematodes applied to the soil will destroy the larval stage, reducing root feeding and helping to prevent the next generation of adults from emerging. Diatomaceous earth can be dusted over plants to control the number of feeding adults. If pest populations become intolerable, spot treat with botanical insecticides as a last resort.
LEAFFOOTED BUG
These large plant-eaters have thick thighs, often with spikes on them. They make a loud noise when they fly and can emit an odor when bothered. Most species are found in the south United States.
Identifying Colors: brown; white; gray; black; yellow; orange
The immature stages (known as nymphs) of this insect are spindly, soft-bodied and bright orange-red in color. Very young nymphs stay tightly clustered as a family unit. The adult stage of the leaf-footed bug is brown, oblong and nearly an inch long. The species most common to this area has a distinctive white band extending across the front wings. The hind legs have a leaf-like shaped area from which the insect’s name is derived.
Leaf-footed bugs have a needle-like, piercing-sucking mouthpart through which they suck plant juices. The puncture made is what caused the spot and the deformation that you have observed. While making the puncture, a toxin is injected into the fruit. If you peel back the skin, you will see that this discolored area is more than superficial. The tissue below the skin is a somewhat corky or spongy mass of silvery white cells.
This damage is serious for commercial fresh market tomatoes and whole pack processing tomatoes because it renders the fruit unmarketable. However, if the fruit was of high quality prior to damage, the processor might cut out the spots and use the remaining tomato as canned pieces. The undamaged portion of the tomato in a home garden certainly can be consumed, if desired.
Leaf-footed bugs are also serious pests of other crops including beans, cowpeas, eggplants, okra, citrus, and pecans. Adult leaf-footed bugs migrate from weedy areas into tomato plants, particularly when the fruit has started to ripen. This is why you typically do did not see damage early in the season but you did see damage later in the harvest season.
Leaf-footed bugs are difficult to control. Weedy areas, such as fence rows and ditch banks, serve as shelters for these insects during the winter season, and when tomatoes and other host plants are not available. Therefore, to eliminate such areas near your garden or to keep weedy areas closely mowed would be beneficial.
It is important to observe your garden on a daily basis. Should you spot leaf-footed bugs, you might handpick the bugs, especially early in the season and when the very young nymphs are tightly clustered. You should use gloves because of the odor they will emit when handled and you should drop them into a can of soapy water.
MEXICAN BEAN BEETLE
The Mexican bean beetle (Epilachna varivestis) is one of the most destructive insect pests of beans in the Eastern United States and portions of the Southwest. Both the adult and the larval stages feed on the undersides of the leaves, and sometimes will attack young pods and stems. As a result of feeding, only the veins are left, giving the leaves a lacy appearance. Damage is most severe in July and August and occurs on all bean varieties, including bush, pole, lima, pinto, navy, kidney, soybeans, and cowpeas. Bush varieties seem to be attacked more readily than pole varieties.
Adult beetles (1/4 inch long) are similar in appearance to large ladybugs. They are yellow to coppery-brown in color, oval in shape, and have 16 black spots on their wing covers. Larvae (1/3 inch long) are fat, hump-backed grubs with fuzz or spines, arranged in six longitudinal rows on their backs. They are orange to yellow in color and attach themselves to leaf surfaces.
Adults overwinter in plant debris and other protected areas and emerge when the weather warms up in mid-to-late spring (usually when beans begin sprouting). After feeding for 1 to 2 weeks females begin to deposit yellow eggs in groups of 40 to 60 on the undersides of bean leaves. Larvae hatch in 5 to 14 days and feed for 2 to 5 weeks before pupating on the undersurfaces of leaves. Adults emerge 3 to 10 days later and live from 4 to 6 weeks. The period from egg to adult is about 30-70 days, depending on temperature. There are several generations each growing season.
Since damage is most severe during summer months, consider planting early maturing bean varieties to reduce pest problems. Hand pick the adults and immature stages from plants and drop them in a pail of soapy water. Also, remove the bright yellow eggs laid in clusters on the undersides of leaves. Floating row covers can be used as a physical barrier to keep beetles and grubs from damaging plants. Beneficial insects, such as ladybugs, lacewing, and minute pirate bugs, are all voracious predators of both the egg and young larval stage. Apply diatomaceous earth to plants and/or spot treat with insecticidal soap to keep pest populations under control. Thorough coverage of both upper and lower leaves is necessary for control. If pest levels become intolerable, spot treat with botanical insecticides as a last resort. Treatments should be repeated in 7-10 days if additional beetles are found. Remove garden trash and other debris shortly after harvest to reduce over-wintering sites.
SQUASH BUGS
The adult squash bugs are strong fliers and migrate to fields and gardens in early summer. Squash bug eggs are shiny brown and elliptical, attached in groups to the underside of leaves.
Squash bugs are among the more difficult insects to control. This is in part due to the difficulties of spraying large plants such as squash. But squash bugs are also inherently resistant to most insecticides.
Adults overwinter and seek shelter under dead leaves, vines, rocks and other garden debris. As temperatures begin to warm in the spring (late May and early June), squash bugs emerge and fly into gardens where they feed and mate. Egg laying soon begins and continues until midsummer with females depositing small brown eggs usually on the undersides of leaves. Eggs hatch in one to two weeks and the young nymphs disperse quickly to feed. Nymphs pass through 5 instars requiring up to 6 weeks to develop into adults. There is typically one generation per year.
Note: Squash bugs give off an unpleasant odor in large numbers or when crushed.
Damage is caused by the feeding of the insects which use their piercing mouthparts to lacerate and destroy pockets of plant tissue. As infestations progress, large areas of the plant become girdled and wilt. Feeding on the fruit also occurs and the sunken wounds are ready entry courts for rots. Although hard "winter type" squashes (including pumpkins) are particularly susceptible, zucchini and other summer squashes are also damaged.
An optimal timing for managing squash bugs involves early season control. A spray applied when the first eggs are observed and again 10-14 days later should provide good season-long control. This approach has the further advantage of having to treat fairly small plants so coverage should be good.
However, it may be possible to further restrict the amount of insecticide needed by targeting the applications to the base of the plant. During the day, squash bugs usually seek shady cover and aggregate around the base of the plant. In addition, a few applications of diatomaceous earth around the plant base were also effective.
Management around the base of the plant seems to be very important in other respects. When mulch is provided, an additional source of cover, squash bug injury increases. Therefore, it appears that a better approach is to try to open up the area of the plant base through plant training to reduce its suitability to squash bugs.
Plant resistant varieties when available. If only a few plants are affected, handpick all stages from the undersides of leaves. Some gardeners prefer to place boards or shingles on the ground near host plants. Used as a nighttime shelter, they make excellent traps for morning collecting. Floating row covers are extremely effective when placed on seedlings and left in place until plants are old enough to tolerate damage. Diatomaceous earth, a natural pesticide made from the fossilized shells of one-celled organisms called diatoms, is abrasive to many insects and can be dusted over plants to provide control. If pest levels become intolerable, spot treat with botanical insecticides. Roto-till or dispose of infested crop remnants shortly after harvest to reduce overwintering adults.
Tip: Researchers at Iowa State found that mulching with newspaper and hay, before putting tightly secured row covers on gardens, provided very effective control of both weeds and pests.
SQUASH VINE BORER
The squash vine borer is a key pest of winter squash, gourds and pumpkins. Unfortunately, it is usually noticed only after it has done its damage. Symptoms appear when a long runner or an entire plant wilts suddenly. Infested vines usually die beyond the point of attack.
Sawdust like frass near the base of the plant is the best evidence of squash vine borer activity. Careful examination will uncover yellow brown excrement pushed out through holes in the side of the stem at the point of wilting. If the stem is split open, one to several borers are usually present. The caterpillars reach a length of 1 inch and have a brown head and a cream colored body. Winter squash, particularly 'Hubbard', are most susceptible to damage while 'Butternut' is somewhat resistant.
The adult squash vine borer is a stout dark gray moth with 'hairy' red hind legs, opaque front wings, and clear hind wings with dark veins. Unlike most moths, they fly about the plants during the daytime, appearing more like a paper wasp than a moth.
This insect overwinters as a full grown larva or a pupa one to two inches below the soil surface. If it has not already done so, the larva pupates in the spring. Adult moths begin to emerge about the time the plants begin to run, and moth flight continues through mid August.
The small brown eggs, laid individually on leaf stalks and vines, hatch in seven to 10 days. The newly hatched larva immediately bores into the stem. A larva feeds for 14 to 30 days before exiting the stem to pupate in the soil.
Recent research has identified squash bug as a vector for the newly named Cucurbit Yellow Vine Disease (CYVD). Once squash plants start to yellow from infection with this virus, there is very little that can be done. The viral disease, which shows up soon after transplanting, has been reported in Kentucky, Oklahoma, and Texas, and is suspected in Ohio. The organism has been identified as Serratia marcescens.
Cultural practices such as timing of plantings, choice of cultivars, and field sanitation practices are examples of first-line, systemic strategies for pest management. Mulches are known to harbor squash bugs. Helpful sanitation measures include removal of plant debris, soil incorporation of cucurbit crop residue, and removal of old boards and other overwintering sites. These practices can prevent squash bug infestations.
Annual rotation to non-curcubit crops is a primary step toward cultural control of squash vine borer and the squash bug. However, you should be aware that the squash vine borer adults are strong fliers and have been known to find squash fields as far as one-half mile from their emergence site in another field.
Vine residues should be destroyed as soon as possible after harvest to prevent late larvae from completing their lifecycle. Consider planting cover crops or other measures that minimize the risks of erosion or compaction of bare soil.
Mechanical and physical practices provide a second line of defense against pests. Such practices include the use of barriers and non-synthetic lures, traps, and repellents such as kaolin clay products. It also includes developing habitat for beneficial predators and parasites.
Researchers found that mulching with newspaper and hay, combined with tightly secured row covers on the plots provided very effective control of both weeds and squash bugs in pumpkin (C. pepo). The row covers apparently excluded squash bugs, preventing them from entering to lay eggs.
Some products acceptable in organic vegetable production that are effective against squash bugs include diatomaceous earth and neem oil.
STINK BUGS
Stink bugs, also referred to as shield bugs, are a group of flying insects belonging to the Pentatomoidea family of the order Hemiptera. They secrete a foul smelling liquid from the gland located between the first and second pair of legs. This liquid is released as a defense mechanism to protect from the predators. There are several species of stink bugs, some of which are commonly found all over the world. In general, they are dull in color, measuring about ¼ inch to ½ inch in length. Commonly exhibited colors of stink bugs are gray, brown, blue, green and black.
The habitat of stink bugs include meadows, garden, flower beds, fields and shrubs. They are active from spring through fall season. Many species of stink bugs are destructive and cause serious damage to certain crop families such as mustard, cabbage, rice and cotton. At times, they cause discoloration of the fruits and vegetables. Tomatoes may be pockmarked or misshapen. Beans and peas may be discolored or bad taste. Some are beneficial and useful for the biological control of pests.
Most are plant feeders (a few are predators). Farming areas can yield good numbers in crops like cabbage, cotton, etc. or in nearby roadside vegetation. Many species come to lights at night. Adult stink bugs of various species are active from spring through late fall. To keep them alive in the classroom, give the bugs well washed fresh green beans.
THRIPS
Thrips are small insects, only about 1/20", but they can cause a lot of damage. At maturity, they are yellowish or blackish with fringed wings. Nymphs have a similar shape but lack the wings. They are usually yellowish to white. Thrips are poor flyers. As a result, damage often occurs in one part of the plant then slowly spreads throughout it.
Thrips feed in buds, folded leaves, and other unexposed areas of plants. They feed by sucking juices from the plant causing stippling, or small scars, on leaves, flowers and fruit. This results in stunting of the plant, leaf distortion and premature leaf drop. Flowers may be deformed and fail to open properly. Petals may show brown streaks and spots. Their excrement is black and shiny, which may be a clue to their presence. In addition to this physical damage, thrips also transmit tomato spotted wilt virus and impatiens necrotic spot virus, for which there is no control.
Control of thrips is difficult. To look for their presence, shake the plant out over a sheet of white paper.
Here are a few ways to control thrips:
Remove thrips by applying a strong stream of water to the affected plant.This is one time you will want to use overhead watering as it kills many of the thrips.
Placing aluminum foil mulches under the plants has been found in some instances to disorient the thrips.
Remove and discard affected blossoms and plant parts.
Thrips prefer tender new growth. Avoid excess pruning which may stimulate new growth.
Avoid planting near dry, weed or grassy areas. Thrips migrate from these areas into the garden.
Products that have been somewhat successful are: horticultural oils, insecticidal soaps, neem oil.
TOMATO HORNWORM
Tomato/tobacco hornworms are the largest caterpillars found in this area and can measure up to 4 inches in length. The prominent "horn" on the rear of both gives them their name.
The size of these garden pests allow them to quickly defoliate tomatoes, potatoes, eggplants, and peppers. Occasionally, they may also feed on green fruit. Gardeners are likely to spot the large areas of damage at the top of a plant before they see the culprit. Hornworms are often difficult to see because of their protective coloring. Not much for the heat of direct sunlight, they tend to feed on the interior of the plant during the day and are more easily spotted when they move to the outside of the plant at dawn and dusk
The tobacco hornworm larva (Manduca sexta) is generally green with seven diagonal white lines on the sides and a curved red horn . The tomato hornworms (Manduca quinquemaculata) have eight V-shaped marks on each side and their horn is straighter and blue-black in color . These "hornworms" are the larvae of hawk or sphinx moths, also known as hummingbird moths. The tobacco hornworm is the most commonly seen of the two, but both can be found in this region and may even be present on the same plant.
The presence of the hornworm may also be noticed because of the large, black droppings (frass) that accumulate on the ground beneath the affected plants.
Because they are so large hornworms are most often controlled in home gardens by handpicking. Once removed from the plant, they can be destroyed by dropping them into a bucket of soapy water. Beneficial insects including lacewings, braconoid and trichogramma wasps, and ladybugs attack the eggs. For best results, make releases when pest levels are low to medium. If populations are high, use a least-toxic, short-lived natural pesticide to establish control, then release predatory insects to maintain control. Both Dipel Dust (Bacillus thuringiensis, var. kurstaki) and Monterey Garden Insect Spray (spinosad) are very effective, especially on young caterpillars (larvae). If pest levels become intolerable, spot treat with botanical insecticides. Roto-tilling after harvest destroys overwintering pupae in the soil. This is especially effective since pupae are large and not buried very deeply in the soil. Results have shown that greater than 90% mortality is caused by normal garden tilling.
Note: If you have caterpillars that have parasitic wasp cocoons attached to them, don't destroy them! Collect them instead and allow them to eat unwanted or volunteer tomatoes until the wasps hatch inside. Now you've got an army of free, natural predators to work for you.
WHITEFLIES
Common on houseplants and in greenhouses, the whitefly (Trialeurodes vaporariorum) is a sap-sucking insect that is often found in thick crowds on the undersides of leaves. When infested plants are disturbed, great clouds of the winged adults fly into the air. Both nymphs and adults damage plants by sucking the juices from new growth causing stunted growth, leaf yellowing, and reduced yields. Plants become weak and susceptible to disease.
Like aphids, whiteflies secrete honeydew, so leaves maybe sticky or covered with a black sooty mold. They are also responsible for transmitting several plant viruses. In southern and coastal states, this pest will be found year-round in outdoor gardens. In northern areas year-round infestations are possible only indoors. Host plants include more than 250 ornamental and vegetable plants. Citrus, squash, poinsettia, potato, cucumber, grape, tomato, and hibiscus are commonly infested.
Whitefly adults (1/16 inch long) are moth-like insects with powdery white wings and short antenna. They are easily recognized and often found near the tops of plants or on stem ends. Wingless nymphs are flattened, oval and almost scale-like in appearance. After the first instar, or crawler stage, they settle down and attach themselves to the underside of leaves and begin feeding.
Whitefly nymphs overwinter on the leaves of host plants. In late spring adult females deposit 200-400 eggs in circular clusters on the undersides of upper leaves. The eggs hatch in 5-10 days and first instar nymphs, which resemble small mealybugs and are called crawlers, move a short distance from the egg before flattening themselves against the leaf to feed. The remaining nymphal stages (2nd, 3rd and 4th) do not move. A non-feeding pupal stage follows and within a week, young adults emerge to repeat the cycle. There are many generations per year. Whiteflies develop from egg to adult in approximately 25 days at room temperature. Adults may live for one to two months.
Note: All of the immature stages are easily overlooked. They are usually pale, almost translucent, and blend with the color of the leaf to which they are attached. Superficially they are similar to several scale insects.
Yellow sticky traps are helpful for monitoring and suppressing adult populations. If found, use the Bug Blaster or hose off plants with a strong stream of water to reduce pest numbers. Natural predators of this pest include ladybugs and lacewing, which feed on their eggs and the whitefly parasite which destroys nymphs and pupae. For best results, make releases when pest levels are low to medium. If populations are high, use a least-toxic, short-lived natural pesticide to establish control, then release predatory insects to maintain control. Insecticidal soap, neem oil, and botanical insecticides can be used to spot treat heavily infested areas. Spot treat with insecticidal soap or botanical insecticides if population become intolerable.
Tip: Insecticidal control can be difficult because the insect is resistant to many synthetic insecticides. However, horticultural oils, which work by smothering insects, are very effective on all stages of this pest.
Note: Ants feed on the honeydew that sucking insects produce and will protect these pests from their natural enemies. An application of Tanglefoot Pest Barrier to the stalks of roses and other woody plants will help keep ants away.
