Variation found in adult bean leaf beetles Adult bean leaf beetles overwinter beneath plant debris at the edge of woodlots or fence rows near bean fields. They become active in the spring when temperatures reach 50 F, and migrate to alfalfa, clover, and occasionally to various weeds. Bean leaf beetles are strong fliers and move to soybean fields when the plants emerge. Females lay an average of 40 clusters of 10-30 eggs per cluster. The eggs are laid over a period of 3 to 4 weeks in the top 2 inches of soil under bean plants.
Temperature impacts bean leaf beetle development.
Eggs hatch in 5 to 7 days at 75 F, but may take 3 weeks to hatch at lower temperatures. The time from egg hatch to pupation is 15 to 16 days at 75 F, and 50 days at 65 F. Larvae remain in the soil, first feeding on root hairs, then nodules, as they progress through three instars. Larval mortality can be attributed to inadequate soil moisture, poor nodule development, and natural enemies. Pupation takes place in earthen cells below the soil surface. Back to Top Damage Bean leaf beetle damage of economic importance is usually caused by the adult, although the larvae feed on bean roots.