- Potential for yield losses exist in early-planted soybeans and in fields that are isolated from other soybean fields.
- Fields at risk should be monitored closely after planting.
- Control may be accomplished with use of seed treatments as well as foliar insecticides.
Impact on Your Crop
- The potential for economic damage may occur when bean leaf beetle (BLB) feeding damages the growing point or cotyledons of soybean before the unifoliate leaves emerge.
- Yield losses may also occur when BLB feeding results in excessive defoliation (30-50% or more) of pre-bloom soybean.
- BLB can transmit bean pod mottle virus (BPMV), with early infection posing the greatest risk of potential yield loss.
- Scout for adult BLB as soon as soybeans emerge (Figure 1).
- Seedling stage scouting requires a determination of the number of beetles per foot of row or per plant. Drop cloths or sweep nets can be used, and sampling should occur at five different locations throughout a field. Also note the extent of defoliation when counting beetles.
- Management thresholds vary by region and recommendations can be found in your local University Extension publications or by contacting your Extension entomology specialist.
- Insecticidal seed treatments help protect seedlings from early-season BLB feeding.
- If an insecticide seed treatment was not used, a foliar insecticide treatment may be warranted when BLB feeding appears to be injuring or clipping the cotyledons and growing points of soybean, or when economic thresholds have been reached.
- For prevention of BPMV transmission, one approach is to use a seed treatment or foliar insecticide to protect seedlings from overwintering adults followed by a foliar insecticide targeted against first generation adults.
Hunt, T. and Jarvi, K. 2012. Scout early emerging soybeans for bean leaf beetles. University of Nebraska-Lincoln CropWatch. http://cropwatch.unl.edu; Davidson, D. 2016. Watch for bean leaf beetles. Illinois Soybean Advisor. http://ilsoyadvisor.com; Varenhorst, A. 2017. Bean leaf beetles: early season soybean defoliators in 2017. South Dakota State University Extension IGrow publication. http://igrow.org Web sources verified 02/01/18.