Look for adults in late June through September. Timing may vary, depending on geographic location. Adults tend to congregate on plants, feeding between the leaf veins and causing leaves to appear lace-like or skeletonized. Japanese beetle adults feed on a wide variety of herbaceous perennials.
Japanese beetles are attracted to plants that have been previously damaged, so it is important to control beetles early. The use of pheromone and bait traps is not recommended because this will attract more beetles from surrounding areas and result in greater damage to plants. Small numbers of Japanese beetle adults can be hand picked. Contact insecticides may be applied as soon as adults are apparent. Note that many contact insecticides are harmful to bees, beneficial insects and mites.
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The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the AgBioResearch, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.