E-21
DEPARTMENT OF ENTOMOLOGY
vegetable insects

CONTROLLING INSECTS IN THE HOME VEGETABLE GARDEN
David L. Matthew, Extension Entomologist

DETERMINING IF AND WHEN TO TREAT
Clean cultivation along with frequent, close inspection of plants may make insecticide treatment unnecessary in many home vegetable gardens. For instance, early-detected caterpillars, loopers, horn-worms, and large beetles can often merely be picked from plants and destroyed before they cause problems. (There is little evidence, however, to verify the beneficial effects of companionate plants for pest control.)

Even if insecticide use is warranted, many vegetables do not need to be treated on a regular basis. In fact, when used improperly, some materials might cause more harm than good. One example would be with the use of carbaryl (Sevin), an excellent insecticide for the home garden.

Carbaryl is used primarily to control chewing insects, such as beetles and caterpillars, found on vegetables. It does not kill aphids, spider mites, whitefly, or cabbage looper; but it does kill lady beetles and some other natural enemies that help to control these pests. Thus, early and frequent use of carbaryl on tomatoes, eggplant and melons may lead to severe problems later by killing the natural enemies of aphids, mites, and whitefly without affecting these pests themselves.

On cabbage and its relatives, carbaryl may be used early to control flea beetle, imported cabbage worm, and diamondback moth larvae; but it will not control the cabbage looper, which appears in mid-July. Therefore, a switch should be made at this time to Bacillus thuringiensis, rotenone, or endosulfan. If early insect control is necessary on these crops, use of a combination product, or products containing malathion or diazinon (both of which give some aphid, mite, and whitefly control) will help to avoid later problems.

SELECTING THE "RIGHT" INSECTICIDES
General Purpose Materials. Ready-to-use, "general purpose" garden sprays and dusts usually contain several ingredients to control the principal insects and diseases of vegetables or ornamentals. The insecticides most commonly included are methoxychlor, rotenone, carbaryl, pyrethrins, or malathion, sometimes with a fungicide for disease control such as captan. If applied according to directions, general purpose mixtures will give adequate protection in most cases.

Special Use Materials. For control of specific vegetable insects, Table 1 lists most of the common ones and the insecticides to use against them. Each material should be applied according to package directions and/or mixed as shown in Table 2. For help in identifying vegetable garden pests, see Purdue Extension Publications E-65 and E-88.

MAKING PROPER APPLICATION
Either spraying or dusting, properly done, should give adequate control of insects. If dusting, plants need only the lightest coating of dust, but that coating must be on both upper and lower plant surfaces. Because of this, shaker-can dusters usually do not do an adequate job. Squeeze or plunger dusters probably are better, as are aerosol dusters if kept agitated while dusting. Dusts will usually be more expensive per ounce of active ingredient than will spray formulations.

When spraying, again both upper and lower surfaces must be treated. Sprayer pressure must be sufficient to roll leaves over for coverage. Hose-end, trombone, and compressed air (pump) sprayers are all adequate, with compromises to be made between convenience, cost, and effectiveness. Aerosol cans

COOPERATIVE EXTENSION SERVICE • PURDUE UNIVERSITY • WEST LAFAYETTE, INDIANA 47907