NGA Articles: Vegetable Garden Pest Control

Vegetable Garden Pest Control (cont)

By: National Gardening Association Editors

Eight Vegetable Garden Insecticides

Here are the insecticides you are most likely to need in a vegetable garden. Note that many others are available and sometimes recommended, but these are the safest and most effective for most home gardeners.

Name Use against How it works; how long it lasts How to use it
Bt. Toxic primarily to caterpillars Cabbageworms and cutworms. Use B. t. tenebrionis for Colorado potato beetle. Bacterial toxin; causes caterpillar death usually within 24 hours. Dissipates in 2 days or less. Available as spray or dust. Apply late afternoon and reapply after rain. Mix with insecticidal soap for better coverage.
Diatomaceous earth (DE). Toxic primarily to soft-bodied insects, snails and slugs Discourages aphids, juivenile Colorado potato and bean beetles, leafhoppers, and thrips. Sharp-edged diatom skeletons scratch insect exteriors, causing them to dry out. More effective combined with pyrethrins. Use natural grade DE, not the kind used in swimming pool filters. Wear dust mask.
Particle film dust. Coats leaves and repels insects Japanese beetles, tarnished plant bugs, and Colorado potato beetles. Specially refined kaolin clay uses microscopic particulates to form barrier film on leaves. Apply with pressure sprayer. Mix with Bt or pyrethrins.
Horticultural oils. Toxic to many insects and mites Kills aphids, corn earworms, leafhoppers, spider mites, whiteflies. Kills pests by suffocating them. Use highly refined summer oils. Do not apply to drought-stressed plants, or on hot, cold, or very humid days.
Insecticidal soap. Toxic mostly to soft-bodied insects Kills aphids, earwigs, grasshoppers, Japanese beetle adults, leafhoppers, spider mites, whiteflies. One of the safest insecticides. Fatty acids destroy the cellular membrane of insects on contact. Mix with warm soft water and be sure to cover both sides of leaves. Can burn leaves during hot weather.
Neem. Toxic to juvenile forms of some pests; also a repellent Kills juvenile aphids and Colorado potato beetle. Repels whiteflies, Japanese and Colorado beetle adults. Affects growth hormones of some insects causing them to stop feeding. Effect lasts about 1 week. Apply liquid spray morning or evening with humidity is high.
Pyrethrins Toxic to a broad spectrum of pests Controls most vegetable pests included flea, potato, and bean beetles. A nerve toxin, often combined or DE. Degrades rapidly. Apply dust during cloudy weather or early evening.

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