These destructive insects are often found feeding in large numbers on pumpkins, cucumbers and winter squash. Here’s how to get rid of squash bugs organically.
Well known and widely distributed in North America, the squash bug (Anasa tristis) is a potential problem on all vegetable crops in the cucurbit family. They are often found in large numbers and tend to congregate in clusters on leaves, vines and fruits. Injury is caused by both nymphs and adults sucking sap from the foliage and vines of squash, pumpkins, cucumbers and other closely related plants. As they feed, they inject a toxic substance that causes host plants to wilt. When feeding is severe the leaves become black and crisp and die back. This condition is often referred to as “anasa wilt” which closely resembles bacterial wilt, a true plant disease. Smaller plants may be killed, while larger plants often recover once feeding stops. Heavy infestations may prevent fruit from forming.
Adults (5/8 inch long) are dark brown or gray in color which keeps them well camouflaged around plants. Known as true bugs, they have a hard shell with a long shield-like shape, two pairs of wings, and sucking mouthparts that originate from the tips of their head. Spider-like nymphs (1/10 inch long) are voracious and feed together in clusters or groups. When young they are whitish green or gray in color with red heads, legs and antennae. As they mature, they become grayish-white with dark legs.
Note: Squash bugs give off an unpleasant odor in large numbers or when crushed.
Adults overwinter and seek shelter under dead leaves, vines, rocks and other garden debris. As temperatures begin to warm in the spring (late May and early June), squash bugs emerge and fly into gardens where they feed and mate. Egg laying soon begins and continues until midsummer with females depositing small brown eggs usually on the undersides of leaves. Eggs hatch in one to two weeks and the young nymphs disperse quickly to feed. Nymphs pass through 5 instars requiring up to 6 weeks to develop into adults. There is typically one generation per year.
Note: Because of the long egg laying period, all stages of this garden pest occur throughout the summer.
Squash Bug Control
Plant resistant varieties when available. If only a few plants are affected, handpick all stages from the undersides of leaves. Some gardeners prefer to place boards or shingles on the ground near host plants. Used as a nighttime shelter, they make excellent traps for morning collecting. Floating row covers are extremely effective when placed on seedlings and left in place until plants are old enough to tolerate damage. Diatomaceous earth, a natural pesticide made from the fossilized shells of one-celled organisms called diatoms, is abrasive to many insects and can be dusted over plants to reduce numbers. If pest levels become intolerable, spot treat with an organic insecticide. Roto-till or dispose of infested crop remnants shortly after harvest to reduce overwintering adults.
Tip: Researchers at Iowa State University found that mulching with newspaper and hay, before putting tightly secured row covers over gardens, reduced both weeds and pest numbers.