Thursday, June 14, 2012

Japanese beetles are hungry

Since I first mentioned seeing Japanese beetle about two weeks ago, I've had many reports of significant numbers around the state of Iowa. There have been a few look-alikes emerging, too, and a recent ICM News article can help with identification. Of course I have seen them on urban plants, but that is where I would expect to see them in June. I noticed adults feeding in corn, soybean and vineyards this week.

Normally, Japanese beetles feed on corn silks later in the season, but Mark Licht, ISU Field Agronomist, noticed them feeding on the corn leaves. I personally haven't seen this before, but I guess they have to feed on something until the silks come out. I did visit a few farms around Ames today and noticed adults in corn. I don't know if they were feeding or just trying to stay protected from the wind. I also noticed beetles defoliating young soybean. They often aggregate to feed and mate, so individual plants had skeletonized leaves.

Japanese beetles in V8 corn at the ISU Johnson Research Farm. Photos taken 14 June 2010 by Erin Hodgson.

Japanese beetle defoliation is often overestimated in soybean. Although some leaves were heavily skeletonized, the overall defoliation on these V2/V3 plants was <1%. Photos taken 13 June 2012 by Erin Hodgson. 

Japanese beetle feeding and mating on grape leaves at a winery in eastern Iowa. Photo taken 13 June 2012 by Erin Hodgson.

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