How to Identify Squash Bugs
The squash bug is fairly large (over ½-inch long) with a brownish or gray body and flat back. The edges and undersides of the abdomen have orange stripes. They are able to fly, but they often simply walk around on plants. Young squash bugs, or squash bug nymphs, are gray and have black legs. They move quickly and often in groups on the undersides of leaves.
Photo Credit: University of Massachusetts Amherst. Newly-hatched squash bug nymphs are small with black legs and move around in groups.
Squash bugs overwinter in your dead leaves, vines, under boards, and even in buildings. They fly to garden plants to mate as soon as vines start forming, and they lay egg masses on the undersides of the leaves. You’ll find adults beneath damaged leaves and near the plant crown.
Photo Credit: University of Delaware Cooperative Extension. Squash bugs lay small brown eggs on the undersides of leaves.
Squash Bug Damage
These bugs inject a toxin into the plant and suck the sap right out of it with their sharp, sucking mouthparts. This causes yellow spots that eventually turn brown. The leaves will wilt because the damage prevents the flow of nutrients to the leaves, and then they will dry up and turn black, crisp, and brittle. The leaves also sometimes have ragged holes. Smaller plants will die, and squash bug feeding can decimate young fruit.
The wilting can resemble bacterial wilt, which is a disease spread by cucumber beetles (yet another squash pest), so be sure to find the bugs or eggs and identify them correctly.