University of Illinois Extension

University of Illinois Extension

Hort Answers

Insect Damage

Lygus Bug
Lygus species.

Lima beans.


Lygus bugs are spindly legged, small insects, both as nymphs and adults, that move rapidly when disturbed. Adults are 1/4 inch long, brown, flat-topped, with many angular black markings. Nymphs are smaller and greenish, with a few tiny dark spots.

Lygus bugs feed on the blooms of lima beans. Their piercing-sucking mouthparts not only withdraw juices but also inject a toxin. This causes the blooms to blast, reducing yield.

Life Cycle

Lygus bugs overwinter as adults. In the spring they feed on overwintering plants. Eggs are laid in late spring and early summer, and nymphs start to appear shortly after. There are two generations of most Lygyus species in Illinois, with three generations of some species in southern Illinois.

Lygus bugs are common on pigweed seed heads, so check them in the vicinity of the bean field. Do not mow the pigweeds near bean bloom because mowing will cause the bugs to migrate to the beans. Use a sweep net to check for bugs in the beans. Five or more bugs per twenty-five sweeps is enough to warrant treatment.

Related Resources
Home, Yard & Garden Pest Guide
Illinois Commercial Landscape and Turfgrass Pest Management Handbook
U of IL - Distance Diagnosis through Digital Imaging
U of IL - Plant Clinic