Fighting Garden Pests the Organic Way

By Ann Whitman, Suzanne DeJohn, and The National Gardening Association

To manage garden pests without using harmful insecticides you have to know what to look for. Here's a short list of insects that can damage your garden vegetables and flowers and the organic gardening measures for controlling them:

Aphids: These pear-shaped pests pierce holes in plant tissue and suck the juices. Blast them off with a hose; control them with lacewings, ladybugs, or sticky yellow traps.

Aphids tend to congregate on the newest leaves and buds.
Bean leaf beetles: Adult beetles chew holes in bean leaves, and the larvae attack the roots. Control by covering plants with row-cover fabric.

Bean leaf beetle adults chew leaves; the larvae attack plant roots.
Colorado potato beetles: The adults lay orange eggs on the undersides of eggplant, tomato, and tomatillo leaves. Handpick adults, and crush egg clusters.

Control Colorado potato beetles by encouraging spiders, lady beetles, predatory stinkbugs, and tachinid flies.
Cucumber beetles: Cucumber beetles chew holes in the leaves, roots, and fruit of squash, corn, beans, and peas. Control by covering plants with row covers until they flower.
Cutworms: Cutworm caterpillars chew through the stems of young plants at night and spend the day curled in the soil. Control by picking the caterpillars from the soil and spraying Bt. Wrap the plant stems with strips of newspaper that extend below the soil surface.
Imported cabbage moths: These white moths flutter around cole crops. The caterpillars feed on leaves and flower buds, leaving piles of green excrement. Control by handpicking and crushing eggs and caterpillars.
Lace bugs: These insects suck foliage sap, giving the leaves a whitish or yellow blotchy appearance. Look under the leaves for their sticky brown droppings. Hose off insects or spray with horticultural spray oil.
Nematodes: These microscopic, wormlike creatures live in the soil and attack plant roots. Control by rotating vegetable crops.
Root maggots: Small flies of several species lay eggs in the soil near onions, leeks, cole crops, radishes, and carrots. The maggots hatch and burrow into the roots, killing the plant. Control by covering crops with row covers.
Snails and slugs: Control by placing boards in the garden. Lift the traps and sprinkle slugs with a 50/50 mix of ammonia and water.
Spider mites: These tiny arachnids suck plant sap causing leaf discoloration. To control, wash plants with a strong blast of water.
Tarnished plant bugs: Plant bugs pierce the tissues of vegetable, flower, and fruit plants, and suck the sap. Knock insects off plants into soapy water in cool morning or evening hours.

Tarnished plant bugs cause swelling, dead spots, bud drop, and distorted growth.
Thrips: Infested flowers and young fruits look distorted. Leaves have silvery or white discolored patches on them, sometimes speckled with black. Release lacewings, or spray with horticultural oil.
Whiteflies: Infested plants may release clouds of whiteflies when disturbed. Control whiteflies with insecticidal soap or light horticultural oil.