Jeff Hahn, Assistant Extension Entomologist
Squash bugs have been very abundant this summer. They are found occasionally in home gardens, feeding on squash, pumpkins, and other curcubits. Squash bug nymphs are wingless and grayish-white with black legs. As adults, they are dark brown and range from ½ to 3/4 inch long.
It is common for squash bugs to congregate on the underside of leaves to feed. They use piercing-sucking mouthparts to feed on plant sap which can cause yellowish spots on leaves, later turning brown. Squash bugs can cause vines to wilt, turn brown, and then black before completely drying up. Although squash bugs do not often injure plants, crops can be severely damaged when squash bug numbers are high.
Control generally is not necessary late in the season. However, if you are seeing high numbers on the foliage, especially if you have a lot of adults, you should try to treat them. Carbaryl (Sevin) and permethrin (Eight) are available to the public for squash bug control, although they are only moderately effective against these insects. Because squash bugs do have a tendency to congregate together, you can try to handpick them or knock the insects off into a pail of soapy water. This will somewhat depend on the size of your garden and how much time you have as this is labor intensive. Later in the season, after the plants dry up, squash bugs can directly attack the fruit and damage them. Watch for that and treat damaging number of bugs.
Adult squash bugs overwinter under debris on the ground. You can reduce the number of squash bugs that survive in your garden and adjacent areas by clearing out accumulations of leaves, plant debris, brush piles, boards and other moist, protected areas that can give squash bugs favorable sites to hibernate
