Asiatic Garden Beetle

Bryan Jensen, Dept of Entomology and Division of Extension

Although not currently found in Wisconsin, damage from the Asiatic Garden Beetle (AGB) has been noted in several states since 1921.  Most recently in southern Michigan, Ohio and northern Indiana.  Severe damage, including stand loss, has been observed in some areas.  Its spread has not been rapid, however, now might be a good time for a short discussion as we get ready to monitor fields.

AGB is an annual white grub and larvae feed on several different host plants including corn, soybean, alfalfa and potato.  Symptoms in field crops will show up as stunted plants.  Infestations have been more common and severe on sandy soils.

It may be a guess what the seasonal distribution will be in Wisconsin, however, I would expect grub damage to be heaviest in seedling corn and soybean.  Adults are likely to emerge mid-summer and start laying eggs in the soil soon after.  AGB overwinter as early instar grubs and begin feeding on available plant part in spring.

The above ground symptoms will be similar to what you would expect from other species of white grubs.  However, this grub will be easier to identify.  Use some magnification and look for a white “bulb” on each side of the head.  It is the only specie with that characteristic.    Please examine the enclosed pictures from John Obermeyer, Purdue Department of Entomology.  Also, Dr. Chris DiFonze, Department of Entomology, Michigan State University has prepared an excellent Field ID Sheet for Grubs.

Adults AGB are small, compared to our perennial white grubs and don’t normally feed on crops.  They are, however, very attracted to night lights and will feed on several different garden and landscape hosts.

For now, please be aware of a potentially new (for Wisconsin) pest as you prepare to walk fields.  If something just doesn’t “fit”, please contact your county extension agent for diagnostic help.

Photo 1: Clockwise from top, adult, pupae and grub AGB, Photo 2: “Bulb”, a diagnostic feature on grub

Photo credit: John Obermeyer, Purdue University