Japanese Beetles Found in Missouri

University of Missouri’s Pest Monitoring Network is reporting the first Japanese beetle captures of 2026 and calling for growers to begin scouting soybean and corn crops.

“Although trap captures are currently low, these first detections indicate that Japanese beetles are beginning to emerge,” says MU Extension state crops entomologist Ivair Valmorbida. “Economic damage is unlikely at this time, but farmers should begin scouting soybean and corn fields and monitor populations closely so they can determine whether a foliar insecticide treatment is warranted.”

The Japanese beetle (Popillia japonica Newman) is an invasive species in the United States. This species has one generation per year in Missouri, and adults feed on several plant species, including soybeans and corn.

Valmorbida says peak occurrence likely will happen in the next two to four weeks.

Adult Japanese beetles feed on soybean leaves, defoliating the plants. Adults feed primarily on the upper canopy, skeletonizing leaves by consuming leaf tissue and leaving veins intact.

To scout soybeans, estimate the percentage of defoliation at several locations across the field. Because Japanese beetles usually feed on the upper leaves, it is important to estimate defoliation throughout the entire plant canopy, Valmorbida says.

In soybeans, insecticide treatment decisions are based on growth stage and percentage of defoliation, including injury from other defoliators.

Foliar insecticide treatment is recommended when defoliation is expected to exceed 30% before bloom (V1-R2 growth stages), 15% during reproductive growth stages.

In corn, adult Japanese beetles feed on silks during the pollination period. Severe silk clipping may interfere with pollination, resulting in reduced kernel set and potential yield loss, says Valmorbida

Valmorbida says foliar insecticide application is warranted in corn crops if three conditions are met:

There is an average of three or more beetles per ear.

Silks have been clipped to less than half an inch.

Pollination is less than 50% complete.

The Pest Monitoring Network, part of the MU Integrated Pest Management program, offers an alert system for Japanese beetles and other pests. Subscribe to alerts at ipm@missouri.edu.