adult
adult
Identification & Incidence: Both the bronze adult Mexican bean beetle (MBB) having 16 black spots and the spiny larvae stage cause skeletonized foliar injury of soybeans. Egg and pupae stages are also found on the foliage. MBB infestations in Ohio occur primarily in the eastern and southern regions. Severe defoliation generally occurs in late summer when late instar larvae of the 2nd generation reach peak activity.
Sampling: Inspect 5 plants from 5 locations and determine the percent defoliation. Determine the predominant growth stage of MBB.
Economic Threshold: Treatment is warranted when MBB larvae and/or adults are actively feeding and the defoliation is 40% pre-bloom, 15% at pod fill and 25% at full pod to harvest.
Management Options: Rescue treatments should be applied in a timely manner to prevent peak injury caused by late instar larvae. Treatments applied after larvae begin pupating achieve limited results. See chart for insecticides labeled for MBB.