Green pepper plants are fairly hardy against insect pests, but certain species relish pepper leaves and can seriously defoliate the plants. Leaf-destroying pests include specific species of aphids, caterpillars, leafhoppers and beetles. Pest populations vary from region to region, so a major pepper pest in one part of the country may be only a minor nuisance or totally absent elsewhere.
The tobacco hornworm caterpillar is a voracious devourer of pepper leaves, stripping plants bare of foliage within a couple of days. It is a light green caterpillar with a reddish anal horn and seven diagonal stripes on each side, and can grow to be 8.7 cm (3 1/2 inches) long. The fall armyworm and beet armyworm typically eat large holes in pepper leaves. They are green, brown or black moth caterpillars with contrasting stripes running the length of their bodies and are about 2.5 cm (1 inch) long.
Green peppers are prey to certain aphids and leafhoppers that suck the vital juices from plant leaves, causing the leaves to wilt, curl, crinkle and discolour. The green peach aphid is a tiny 3 mm (1/8 inch) yellow-green, soft-bodied insect that attaches itself in groups to the underside of leaves. Populations can explode quickly. The potato leafhopper is a winged green insect pest about 9 cm (3/8 inch) long with yellow or dark green spots. It can fly but prefers to get around by jumping from leaf to leaf. Like aphids, it prefers to suck juices from the underside of leaves. Spider mites can become a problem in hot, dry weather. These tiny insects, about half the size of aphids, look like mini-spiders and suck leaf juices from the underside.
Leaf-eating beetles that infest pepper plants include flea beetles and pepper weevils. Flea beetles are tiny 3 mm (1/8 inch) beetles that are either solid dark or have a pale yellow stripe on each wing cover. They chew tiny round holes in foliage. Pepper weevils are a type of tiny snout beetle, reddish brown to black with a brassy lustre, about one-eighth of an inch long. They chew small irregular holes in pepper plant leaves.
Management of pests requires gardeners to be vigilant. Weekly scouting of the pepper patch is important to detect the first indications of infestation, such as leaf holes and wilting. Pick off caterpillar and beetle pests by hand, and wash aphids and mites off with an insecticidal soap spray. For major infestations, apply insecticides appropriate for the pests infesting peppers. But use pesticides with care. A spray that kills caterpillars and beetles may also kill beneficial insects that prey on aphids, causing a secondary aphid problem.