Colorado potato beetle adultHome gardeners encounter many problems in producing high quality vegetables in back yard gardens including identification of insects that occur there. This slide set is designed to aid home gardeners in learning to distinguish between harmful pests and insects that do no harm or are beneficial.
One of the first tasks is to identify insects found in the home garden. It is also important to understand pest life cycles and to know when insects occur during the season.
Click on thumbnail to get larger view
Colorado potato beetle adult
This is the adult stage of the Colorado potato beetle. It feeds on the potato foliage beginning in early summer but causes little damage itself. Soon after the adults become active, they mate and lay yellow eggs in masses of 10 to 20 on the undersides of potato, eggplant, pepper, and tomato leaves. Handpicking and destroying adult beetles from potato foliage is an effective control measure when just a few plants are being grown.
Colorado potato beetle eggs
These pale yellow eggs become darker as the developing larvae prepare to emerge in 6 to 8 days.
Colorado potato beetle young larvae
Newly hatched Colorado potato beetle larvae are dark in color as they begin feeding on foliage. Soon they appear orange or red as they mature over 2 to 3 weeks. Control measures are most effective applied when the larvae are very small. Sevin applied as a dust or spray is very effective, as are the Neem-based products among the organic choices.
Mature Colorado potato beetle larva
By the time the larvae reach larval maturity, they have caused significant damage to potato foliage and may limit the yield. When the mature larvae finish feeding they crawl to the ground and burrow into the soil to pupate. Some emerge as late summer adults to start a second generation but the numbers of larvae and damage produced are small.
Colorado potato beetle damage
Severe damage can result from uncontrolled potato beetle feeding.
Wireworm adult and larva
Wireworms pose a different type of problem. The adult beetle on the left does no damage except to lay eggs in the soil in late summer that become tiny larvae by the following spring. Larvae feed on many types of roots of annual vegetables or the tubers of potatoes. Three to four years may be needed in the soil for larvae to develop to the mature larva seen on the right in this photo.
Potato damaged by wireworm
Wireworm damage does not occur in every garden. But when it does, this is the type of damage caused in potatoes. Damaged areas may be cut away and the potatoes still used, but wireworm damaged potatoes do not store well.
Bean damage by wireworm
Wireworms also damage young bean seedlings causing death of the plant. When this is widespread in a garden, the beans will need to be replanted.
Earwig and damage
Earwigs cause little damage to beans and usually do not require control. Damage is shown here.
Mexican bean beetle
Mexican bean beetles are a serious pest in Idaho and must be kept from commercial growing areas. Adult beetles are shown in the upper left and lower left. They are pale yellow with 8 black spots on each wing cover. Eggs are laid on the leaf and soon hatch into the spiny yellow larvae seen in the lower right. Larval feeding damage can be seen near the center in the upper right.
Cutworm larva and adult
Cutworms are soil-borne caterpillars that feed on seedlings near the soil line or on leaf tissue and bean pods as the plant develops. An adult miller moth is shown in the inset photo.
Root maggot and damage
Some vegetables are susceptible to damage from root maggots. This includes radishes, turnips, and onions as well as the roots of cabbage and corn.
Cole crops damaged by maggots
Cabbage, cauliflower, and broccoli can also be severely damaged by the cabbage maggot.
Maggots
Onion maggot, cabbage maggot, and seed corn maggot affect many vegetables. All look very similar to the maggot shown here.
Maggot fly
The adult fly lays eggs in the soil near young plant seedlings and newly hatched larvae enter the soil and feed on the plant tissue.
Imported cabbage worm larva
The main caterpillar pest of cabbage and its relatives is the imported cabbage worm, a light green, velvety appearing caterpillar.
Damaged cabbage
This cabbage plant has been damaged by imported cabbage worm feeding. (Inset: When a cabbage or broccoli plant is left unprotected, damage can be severe.)
Imported cabbage worm adult
This is the adult butterfly that lays the eggs that hatch into damaging caterpillars on the leafy vegetables. It does no damage itself. Spotting them around the garden should be a warning that the damaging caterpillars will not be far behind.
Corn earworm
Insects that affect corn include the corn earworm, aphids, wireworms, and earwigs. The corn earworm is the most important pest of garden corn and can be a serious pest in some years. One egg is laid by the adult moth on the green silk of a developing ear. The emerging larva penetrates into the ear and feeds on developing kernels resulting in the damage seen here.
Aphids
Several species of aphids may be found on corn and many other garden plants. They cause considerable concern from home gardeners. Usually they occur after corn is well developed and the damage is unimportant.
Squash bug
The main pest of squash and pumpkins is the squash bug. This pest feeds on the main stem eventually killing the entire plant. The adult squash bug is about 3/4 inch long (upper left). Eggs are laid on the underside of the squash plant leaves (upper right and lower left). Emerging nymphs feed on the base of the plant injecting their toxic saliva resulting in wilted leaves and dead plants (lower right). Winter squash and summer squash are susceptible while melons and cucumbers are not usually affected.
Tomato hornworm larva
Tomato plants are relatively free of pest insects except for the tomato hornworm. This large caterpillar is green with white markings and feeds on tomato leaves. Usually the worms do not cause serious damage. Handpicking the larvae from the plants and destroying them is the best control when only a few plants are being grown.
Tomato hornworm adult
Eventually the tomato hornworm caterpillars mature and leave the tomato plant to pupate in the soil. Once development as a pupa is completed, the adult moth emerges to lay eggs and start the life cycle again. These moths are often called hawk moths or hummingbird moths because of their hovering behavior near flowers.
Grasshopper
There are a few insect pests that may be found on many different types of garden plants. Grasshoppers are general feeders and can quickly strip garden plants of foliage when numerous.
White grub larvae and adult
White grubs develop in the soil and feed on root systems and seedlings of many garden vegetables. In well-established gardens, these are rare pests. But when a garden area has recently been plowed from grassy areas, white grubs already in the soil cause considerable damage during the gardening season. The adult beetle is shown in the inset photo. White grubs are the larvae of June beetles and usually require three years to complete development in the soil and emerge as adults.
Cutworm larva and moth
Cutworms are soil dwelling caterpillars that feed on vegetables at or near the soil line.
Beets damaged by cutworms
These beets were damaged by cutworm feeding.
Cutworm adults
These miller moths are the adult stage of several species of cutworms. The adult moths do no damage.
Spinach leafminer larva and damage
The maggot form of a fly is the spinach leafminer. Eggs are laid on the undersides of leaves. Newly hatched larvae burrow between the leaf surface layers. The mines become large blotches as the larvae grow and eat more.
Stinkbug adult
Stinkbugs can feed on developing bean pods and cause deformities or shrunken seed. They can feed on many garden plants (especially mustards) but seldom cause much damage.
Garden Slug
Garden slugs are pests of many garden and other plants. They feed at night and like lots of plant coverage where humidity is high. They leave silvery slime trails where they travel on the plant.
Millipede
Millipedes feed on decaying organic matter but can sometimes damage garden plants. They feed mostly underground.
Millipede damaged carrot
Damage to tuber vegetables by millipedes looks like what is shown on this carrot. They feed in cracks on the tubers making them larger as they go. Chewing marks are not as large as those caused by white grubs or cutworms.