Photo shows the two damaging stages of the beetle.
The adult beetle has 16 black spots on its yellow-brown wing covers. The larvae are spiny yellow grubs.
Larvae and adults feed on the undersurface of bean leaves; only the lace-like structure of the leaf veins remains.
The adult beetles hibernate in protected places. They first appear on bean plants during April and May when they lay yellowish eggs in large clusters on the leaves. The yellow larvae hatching therefrom feed and pupate on the plants from which the newly emerged, light lemon-colored adults appear. Several generations are produced.
Control is difficult because feeding takes place on the undersurface of the leaf. This beetle may infest soybeans throughout the season, but the major buildup usually occurs during blooming and around August 1 or thereafter.
