University of Illinois Extension

University of Illinois Extension

Hort Answers

Insect Damage

Squash Bug
Anasa tristis

3 (1 = rare 5 = annual)
3 (1 = very little damage 5 = plants killed)

The squash bug (Anasa tristis) is a perennial and severe pest of pumpkins and squash; it rarely injures cucumbers and melons in the Midwestern United States.

Plants Affected

Squash bug adults are brown, flat-topped, and 3/4 inch long. The nymphs are gray, flattened, and up to 3/4 inch long. The eggs are reddish brown and laid in clusters on the leaves.

Both the nymphs and adults suck sap out of leaves, stems, and fruit of squash and pumpkin. Feeding by large numbers causes vines to turn brown and black and then dry up. Heavy feeding on the fruits causes them to collapse and be unmarketable.

Life Cycle
Adults overwinter in nearby debris.

Crop rotation will reduce squash bug numbers. Remove debris in the fall to reduce overwintering sites. Treat when the first eggs begin to hatch, usually between June 15 and July 15, if infestations exceed 1 to 1-1/2 egg masses per plant. Treat when squash bugs are young because registered insecticides are not very effective against older nymphs and adults.

Related Resources
Home, Yard & Garden Pest Guide
U of IL - Distance Diagnosis through Digital Imaging
U of IL - Plant Clinic