BEAN LEAF BEETLE

Symptoms: This adult beetle is recognized by having a black triangle between the wing covers, directly behind the head. Some adults have spots. The distinct feature is the black triangle. The adult beetles can only �y a short distance. There are two generations, the second showing the most aggregation in soybeans. Adult beetles will feed on the leaves and pods while their larvae will feed on the roots and nodules. Bean leaf beetles are also the prime vector for bean pod mottle virus.

Life Cycle: The bean leaf beetle will overwinter in soybean residue and in woodlots. If the weather gets cold enough (14 degrees or below for more than 15 minutes), most beetles die. When the beetles colonize within a host crop such as soybeans, they will also lay eggs in the soil near the base of the plants. In roughly a week the eggs will hatch, and the larvae will begin to feed on the soybean roots and root nodules. Then they emerge from the soil in the pupae stage and into the beetle stage around 1,212 growing degree days. Depending on the growing season length, these adults may produce another generation or move to overwintering sites.

Scouting: Scout throughout the season. The bean leaf beetle usually has two generations per year. If it is early in the season, you can walk the �elds and visually inspect the plants by counting the number of beetles. Late season scouting may require a sweep net. Getting a population count will be crucial in making management decisions. The beetles carry bean pod mottle virus, and bean pod feeding is the big e�ect they have on soybeans.

Management Practices: -Bene�cial insects can help reduce the beetle population. -If the �eld has had a history with bean leaf beetles, it would be a good management decision to plant soybeans later in the growing season. -If threshold is met, spray insecticide labeled for bean leaf beetles.