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Japanese beetle

Japanese beetle (Popillia japonica) adults are defoliators of soybean. Severe defoliation of soybean rarely occurs in Iowa, but a complex of pests exist in soybean that may cause concerning levels of defoliation. In corn, the primary concern is silk clipping, which may interfere with pollination. Scouting for Japanese beetle involves predicting activity based on degree day accumulation and looking for Japanese beetles in corn and soybean fields.

Japanese beetle in soybean and corn
Left: Japanese beetles feeding directly on the corn ear. Right: Japanese beetles skeletonizing a soybean leaflet. Photos by Ashley Dean.

An encyclopedia article details Japanese beetle identification, biology, plant injury, scouting, and management. This includes how to track growing degree days and how to sample Japanese beetles.

Japanese beetle encyclopedia article

The Iowa Environmental Mesonet hosts a Pest Forecasting page where growing degree days for Japanese beetle development may be tracked. 

Track Japanese beetle development

Annually, spring scouting alerts for Iowa are posted on the Integrated Crop Management News page. Throughout the growing season, additional updates on Japanese beetle activity may be posted on ICM News or on the Integrated Crop Management Blog page.

If you would like to receive timely alerts of Japanese beetle activity in Iowa via text messaging, sign up for the Iowa Pest Alert Network!