Squash Bugs
Pest · Commonly affects: Summer squash (zucchini), Winter squash, Pumpkins, Cucumbers, Melons, Gourds
The squash bug (Anasa tristis) is a common sap-feeding insect that attacks members of the squash and pumpkin family throughout the United States. Gardeners care because a heavy infestation can wilt and kill young plants outright, and the bugs are notoriously hard to knock back once eggs hatch and nymphs spread across a planting.
How to identify it
Adults are flat-backed, shield-shaped insects about five-eighths of an inch long, dark gray to brownish, with alternating orange and brown edging along the sides of the abdomen. Look on the undersides of leaves for tight clusters of shiny, bronze to brick-red oval eggs laid in the angles between leaf veins. The young nymphs hatch pale green with dark legs and turn gray as they grow, often feeding in groups; crushed bugs give off a sharp, unpleasant odor.
Damage
Squash bugs pierce leaves, vines, and stems with needle-like mouthparts and suck out sap, which disrupts the flow of water and nutrients through the plant. Feeding causes yellow speckling that browns and dries, and heavy attacks trigger a rapid wilting sometimes called anasa wilt, where whole runners or seedlings collapse; developing fruit may also be scarred or fail to fill out.
Prevention
Rotate cucurbits to a different part of the garden each year so overwintered adults emerging in spring do not find host plants waiting nearby. Give plants generous spacing and keep them vigorous with healthy, well-drained soil and steady moisture, since strong plants tolerate feeding better than stressed ones. At the end of the season, pull and compost or remove old vines promptly and clear boards, mulch clumps, and plant debris where adults shelter over winter, and where practical choose vining types like butternut that tend to suffer less than tender summer squash.
How to manage it
Scout leaf undersides one to two times a week and crush the egg clusters or scrape them off with tape, and handpick adults and nymphs into a jar of soapy water in the early morning when they are sluggish. Lay a board or shingle flat on the soil overnight; bugs gather beneath it and can be collected and destroyed each morning. Cover young plants with floating row covers held down at the edges to block egg-laying adults, then remove the covers at flowering so bees can pollinate, and encourage natural enemies such as the tachinid fly parasite and predatory insects by keeping some flowering plants nearby and avoiding broad sprays. Prune out and dispose of badly wilted or heavily infested runners to reduce the population.
General guidance for US home gardens, focused on prevention and non-chemical control. For a confirmed diagnosis and options specific to your area, contact your local Cooperative Extension office. Page updated Aug 4, 2026.