Bean Leaf Beetle, Cerotoma trifurcataHosts: The adults feed primarily on legumes. The most common hosts are snap beans, soybeans, and alfalfa in Oklahoma.
Symptoms: The beetles feed on pods and the underside of bean leaves, and the damage will appear as small, round holes. Damage often occurs as the plants are emerging, and if the beetles are present in large enough numbers, stand reduction can occur. Large populations are also capable of causing extensive defoliation to older stands.
Life Cycle: Adults overwinter in leaf litter or other vegetation, primarily in wooded areas. They become active in April and move to the earliest host plants available. They feed for several days and then mate. Each female lays 175 to 250 eggs in clusters of 12 to 24 in the soil at the base of plants. Eggs hatch in one to three weeks, depending on temperature. Larvae find their way to the base of the stem or roots and feed there for three to six weeks. Mature larvae form earthen cells in which the pupae form. There are two or three overlapping generations, and adults are present almost continuously from April into November.
Description: Adult bean leaf beetles are about 1/5 to 1/4 inch long and yellow, orange, or red in color with a black head and black spots down the center of the back. Normally, there are six black spots which may run together so that it appears only three spots are present, or they may be completely absent. The triangular black mark at the base of the wing covers is always present. The yellow forms can be mistaken for a small spotted cucumber beetle.
Control: Please contact your local county extension office for current information.
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