Japanese Beetles Are Active In Missouri: Time To Scout Soybean And Corn Fields
DR. IVAIR VALMORBIDA
COLUMBIA, MISSOURI
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. The Pest Monitoring Network(https://ipm.missouri.edu/pestMonitoring/) has been capturing Japanese beetle adults since the first week of June, and their numbers have increased in the past two weeks. My lab folks have also been finding adult Japanese beetles in soybeans in several locations across Missouri. I expect the peak occurrence in the next 1-2 weeks.
Soybeans
Adult Japanese beetles feed on the leaves contributing to defoliation in soybeans. Adults feed primarily on the upper canopy, and their feeding causes skeletonization of the leaves by consuming leaf tissue and leaving the veins intact. In soybeans, scouting consists of estimating the percentage of defoliation in the field. Because Japanese beetles usually feed on the upper leaves, estimating defoliation throughout the entire plant canopy is important. Insecticide treatment decisions are based on percent defoliation and growth stage. Foliar insecticide treatment is recommended when insects are present and defoliation is expected to exceed 30% before bloom (V1-R2 growth stage), 10% from pod development to pod fill (R3-R5), and 15% at the R6 (full seed) growth stage.
Corn
In general, Japanese beetles are considered a sporadic pest of corn. Clipping of the silks by adult beetles is the main concern because it can interfere with pollination, and lead to yield reductions.
Foliar insecticide application is warranted if the three following conditions are met:
- There are an average of three or more beetles per ear.
- Silks have been clipped to less than 0.5 inch.
- Pollination is less than 50% complete.
Management
Japanese beetle management is complex because adults are highly mobile. Soybean and corn fields should be scouted periodically to determine whether an insecticide application is warranted.
Find out more:
DR. IVAIR VALMORBIDA
UNIVERSITY OF MISSOURI