No. 13 Article 5/June 22, 2007

Japanese Beetles Have Our Attention

On the heels of our reporting the remarkable numbers of Japanese beetles being captured in traps in southern Illinois (Alert, June 15, 2007), there come even more remarkable numbers. To get it from the horse's mouth (so to speak--sorry, Ron), read the comments from Ron Hines (FS seed agronomist, Growmark southern region) on captures of insects during the week ending June 19. But to capture the essence of his comments, you should know that the trap in Massac County has garnered both a single-day and a weekly record for captures for the history of that trap--68,372 beetles captured on June 17, and 309,352 captured during the week ending June 19. The numbers of Japanese beetles captured at the five other locations (Fayette, Jefferson, Pope, Pulaski, and St. Clair counties) pale by comparison, but most of them captured tens of thousands of Japanese beetles during the same week.

Our reporting of the captures of Japanese beetles in traps in southern Illinois has sparked some competitive spirit. Ryan Cox, south of Elliott in Ford County, used "55 gallon drums, clusters of 5 gallon buckets, and small swimming pools to collect hundreds of thousands of Japanese Beetles" on his farmstead in 2006. Ryan intends to be fully prepared for Japanese beetles again this year.

Several people have reported finding either lots of or just a few Japanese beetles in corn fields, depending on the area of the state, but it is clear that everyone should be on alert. With their silk-clipping behavior, Japanese beetles could wreak havoc in corn fields already suffering from a lack of moisture, assuming the corn plants can even muster silks. The recent rains helped the crops in a lot of areas in Illinois, but some locations still have a significant moisture deficit. And even if the rains helped the corn, the Japanese beetles are still there waiting for pollination. In the meantime, the beetles may very well feed on corn leaves. And don't forget to look for these Japanese beetles in soybeans, too.

The economic thresholds we use for making decisions about Japanese beetle control are 3 or more beetles per ear in corn (plants still pollinating) and 30% defoliation of soybeans before bloom, 20% defoliation during reproductive growth. These thresholds have been in place for many years, so it's difficult to know what changes are necessary for modern hybrids and varieties, higher yield expectations, and/or environmental conditions. Suffice it to say that people who make these decisions will have to use their experiences and best judgment.

Insecticides suggested for control of Japanese beetles in corn and soybeans are presented in Table 1. Please follow all label directions and precautions.--Kevin Steffey

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