Squash Bug

Insect Type:

Nuisance Type:

Plants Affected:

Images of This Insect:

Image of squash bug adults and nymphs

Squash bug adults and nymph.

Image of a lone squash bug on a pumpkin.

Lone squash bug on a pumpkin. Photo from University of Maryland Extension.

The squash bug is distributed throughout the U.S. and is a well-known pest. It attacks all cucurbits and vine crops but is most damaging to squashes and pumpkins. The insect has a disagreeable odor when crushed and is one of many insects known by the nickname "stink bug."

The squash bug adult is 1-inch long, gray-black or brown in color, elongate oval and pointed at the head end. They spend the winter in dormancy in protected locations such as among old vines, under leaves, clods, stones and other debris.

Adults appear on pumpkins and squash when the vines start to run. They may be difficult to see because their color matches the soil and because they are usually hiding under the vines, leaves or clods of dirt. The adults feed on sap from the plant leaves as they lay clusters of a dozen of more, large, brick-red to yellow-brown eggs on the lower sides of the leaves, usually in the angle formed by the leaf veins, or on the stems. Eggs are laid until about mid-summer.

Squash bug nymphs are green when they first emerge from the eggs. They remain in clusters for the first several days. They feed on sap from the plants and grow for a period of 4 to 6 weeks before they reach maturity. Medium to large sized nymphs change to gray or grayish-white color. New adults appear by the end of the summer and may feed on the rinds of unripe fruit before moving to protected locations where they spend the winter. There is only 1 generation per year. Heavy squash bug infestations cause a rapid wilting of the plant. Heavily injured leaves become characteristically blackened and crisp as they die. Small plants may be entirely killed early in the growing season. Larger plants may have isolated damage on certain leaves or runners.

Squash bug populations vary greatly from year to year. Begin checking for eggs and small nymphs during late June. Handpick and discard egg clusters and nymphs as they appear. Use garden insecticides such as Sevin, permethrin or insecticidal soap according to label directions. Sprays are generally more effective than dusts, but must be reapplied frequently. Avoid spraying plants in bloom. If spraying during bloom is necessary, spray at night after honey bees have quit foraging for the day. Remove crop residues in the fall to reduce the number of squash bugs that survive the winter.