Identification & Incidence: Damage to soybeans by bean leaf beetle (BLB) extends from feeding of over wintering adults on emerging seedlings to pod feeding by 2nd generation adults in the fall. Life cycle of BLB includes 2 generations with the peak of the 1st generation in July and the peak of the 2nd generation in late August or September. BLB impact on soybeans tends to increase when most soybeans are planted early.
Sampling: Early in the season sample 5 plants in 5 locations for defoliation. Late in the season sample for both defoliation and pod damage.
Economic Threshold: Treatment is warranted when BLB adults are actively feeding and the defoliation is 40% pre-bloom, 15% bloom to pod-fill and 25% pod-fill to harvest. Treatment may be needed late in the season for pod damage if 10% or more of the pods are being fed upon and BLB is still present.
Management Options: Timely application of rescue treatment will reduce losses in yield and seed quality. Late plantings of soybeans will escape defoliation by over wintering BLB and limit establishment of first generation. See chart for insecticides labeled for BLB.