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.
Adult lygus bugs overwinter in plant litter in fields, woods, timber margins, ditch banks, and rights-of-way. In the spring and early summer, females insert elongate, slightly curved eggs into the stems, leaf petioles, and leaf mid-ribs of a variety of plants. Eggs take 1 to 2 weeks to hatch, depending on temperature. Nymphs develop through 5 stages and take 2 to 4 weeks to reach the adult stage, again depending on temperature. Two to four generations develop each year, with greater numbers in the southern part of the state and in warmer years.
- 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.