A key factor you can use in identification of the adult bean leaf beetle is that all bean leaf beetles have a backwards pointing black triangle on the wing covers behind the head. The larva is almost identical to that of the corn rootworm. Bean leaf beetle larvae are white and segmented, with a brown head and a brown hardened area at the posterior end of the body. Larvae may be found feeding on soybean roots and nodules. Damage Damage to soybeans is usually caused by the adult bean leaf beetle.
Adults feed on cotyledons and leaves, making distinct round holes .
They sometimes feed on pod surfaces but seldom eat through to the seeds. Damage to roots and nodules by larvae has not been shown to significantly reduce yields. If damage is found, try to establish that bean leaf beetles are present. Mid-season plants may be scouted using the shake cloth procedure or the sweep net procedure . Using a fifteen inch sweep net, twenty sweep samples should be taken at each location.