SDSU Predicts Reduced Bean Leaf Beetle Pressure

By Scout Nelson

South Dakota soybean producers may see lower pressure from bean leaf beetles this growing season after cold winter temperatures reduced the survival of overwintering populations. Each year, specialists evaluate winter conditions to estimate how many adult beetles survive and may return to soybean fields in spring.

Information shared by Adam Varenhorst, Associate Professor and SDSU Extension Field Crop Entomologist, along with Philip Rozeboom and Patrick Wagner, highlights how winter weather affects bean leaf beetle survival. Their analysis helps producers understand potential pest risks and prepare management plans for the growing season.

Bean leaf beetles that survive winter emerge in spring and begin feeding on young soybean plants. Heavy feeding can remove leaf tissue and reduce plant vigor, especially when populations are high. Adult beetles are highly sensitive to cold temperatures, particularly when air temperatures fall below 14°F. Extended exposure to these temperatures can cause significant mortality.

Researchers use a survival model developed by Lam and Pedigo to estimate overwintering success. The model measures the accumulation of cold temperatures and considers differences between beetles exposed in crop fields and those protected by crop residue, loose soil, or wooded areas. Snow cover can also improve survival by providing insulation during cold periods.

Based on the 2025-2026 evaluation, predicted bean leaf beetle mortality across eastern South Dakota ranges from 73% to 100%. While some beetles are expected to survive and emerge this spring, populations are generally expected to remain lower because much of the severe cold occurred when little or no snow cover was present.

As a result, bean leaf beetles are not expected to become a major early-season soybean problem in most areas of the state. However, producers are encouraged to continue monitoring fields during spring and early summer. Regular scouting helps identify unexpected infestations before economic damage occurs.

In areas with a history of bean leaf beetle activity, producers may consider insecticide seed treatments at planting. Foliar insecticides may also be used if scouting reveals damaging populations later in the season. Careful monitoring and timely management remain important tools for protecting soybean yields and maintaining crop health.

Photo Credit: istock-urpspoteko