Pests of vegetables are among the gardener's greatest frustrations. Caterpillars, beetlelike bugs, aphids and soil-borne pests wreak havoc by chewing, sucking and burrowing their way through plants, flowers and fruit. Many insects transmit lethal plant diseases, as well. In small gardens, one of the most effective methods of controlling pests is to monitor the plot closely and hand-pick pests when they appear. Rotating plant crops and encouraging beneficial insects are other ways of naturally managing pest insects.
About Vegetable Pests
Vegetable pest insects can be classified into three major categories. Chewing insects are by far the most prevalent and comprise mainly the larvae of adult insects such as moths and beetles. Sucking insects are bugs that drink the sap and fluids from plants, damaging leaves, stems and fruit in the process. Soil pests such as white grubs and nematodes burrow into and through roots of plants, which can impair top growth or decimate crops such as carrots, beets and parsnips.
Common Pest Insects
Some of the most commonly seen pests include the larvae of the imported cabbage moth, a slender, velvety-green caterpillar that feasts on the foliage of cole crops such as cabbage, kale, broccoli and kohlrabi. Corn growers are especially vigilant for earworms, which burrow into developing ears of corn and destroy the growing kernels.
Squash and melons are commonly attacked by cucumber beetles and vine stem borers; the former transmits a lethal bacterium to melons and squash, while the latter are grubs that bore into squash vines at their bases and kill the plants by burrowing through the stems. Tomatoes and potatoes are frequently attacked by tobacco hornworms and the Colorado potato beetle, both of which damage plants by rapidly devouring foliage.
Many university agricultural extension offices offer free, full-color pest guides with photographs of pests as eggs, juveniles (larvae) and adults. Many types of pests feed exclusively at night, making identification and location of these bugs a challenge. Taking a flashlight out and inspecting the garden at night is one way to help identify which pests are helping themselves to your crops. Turning leaves over during the daytime can also help reveal hiding places for pests.
Spotting any type of caterpillar or beetle actively chewing on foliage or congregating on fruit is a clue that you probably don't want it there. The presence of large populations of any type of insect or caterpillar is another indication that they are likely pest insects and should be immediately eliminated.
What universities refer to as "integrated pest management" is a method of controlling pests through a combination of appropriate plant culture, beneficial insects and selected use of pesticides. These principles can be adapted and applied to gardens of any size.
Large-scale farming enterprises sometimes use what are known as trap crops to draw a certain type of pest away from the cash crop and toward another type of plant the pest prefers; that crop can then be destroyed or sprayed and thus also destroy the pest. Judicious use of natural pesticides such as Bacillus thuringiensis (Bt), a bacterial agent; botanical pesticides such as rotenone and neem; or synthetic chemical pesticides such as Sevin can help control especially bad infestations if other avenues fail.
Another element of integrated pest management is to plant a wide variety of vegetable crops, which tends to confuse pests. A wide variety of plant matter also attracts beneficial insects such as ladybugs, mantids, lacewings and other predatory insects, which feed on insect pests. Parasitic wasps are small and rarely seen but are important controls against tobacco hornworms and other types of caterpillars. Assassin bugs and wheel bugs are other predatory insects that come to the garden to feast on soft-bodied prey and small beetlelike pests.