Asiatic garden beetle in southern Michigan

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Purdue recently reported Asiatic garden beetle grub damage in corn in northern Indiana. This week, fields in southern Michigan were also identified with the same pest. Insects don’t see state boundaries. These fields were in southern St. Joseph County. Affected fields had a very sandy soil texture. Stand loss was present at many locations, from high knolls to low areas. Beetles were already pupating or emerging as adults, so within the next few days it will be difficult to determine if fields were damaged specifically by this grub.

Asiatic garden beetle, as the name implies, was introduced from Asia to New Jersey in 1921. It has moved from east to west. In turf, it is still a relatively rare pest in Michigan. Some additional information about Asiatic ground beetle; it has some differences from some of our other grubs.

  • Garden beetles often are in mixed infestations with other species, such as European chafers and Japanese beetles. In southern Michigan, this was the case.
  • Generally, minor turf pests, they are important in nursery and vegetable crops.
  • Adult beetles feed on flowers, weeds, vegetables and presumably field crops.
  • Adults hide during the day and feed at night, actively flying when temperatures are more than 70°F. They often come to lights at night;
  • Eggs are laid in July to October in clusters, preferably in weedy areas. Some weeds are preferred, particularly ragweed.
  • Larvae feed from August into the fall, overwinter in the last stage, and feed again in April. This is when crop damage occurs.

This is yet another species to add to our list of early-season grub pests. Several things have probably contributed to the increase in grub problems, including reduced/no tillage, mild winters, new grub species moving into the state and earlier planting dates. In the future, we will likely be dealing with a complex of species infesting fields in the fall, and damaging crops in April and May.

To identify Asiatic garden beetle, look at the butt end of the grub at the raster pattern (pattern of hairs). Asiatic garden beetle has a “smiley face” pattern of hairs. In southern Michigan, grubs probably already pupated, but adult beetles will be present for the rest of the summer. Adults are reddish brown and barrel-shaped.

Dr. DiFonzo’s work is funded in part by MSU‘s AgBioResearch.

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