Issue No. 14, Article 4/June 29, 2007
Japanese Beetles Will Be With Us for a While
At some point, even the "WOW factor" associated with Japanese beetles seems to lose its impact. Ron Hines, seed agronomist for the FS southern region, once again reported a one-day record catch from his volunteer trapper in Massac County--71,984 Japanese beetles captured during the 24-hour period from June 20 to 21. You can read about the other remarkable numbers of beetles being captured at all six southern sites in "The Hines Report".
It's important to realize that Japanese beetles will be with us for a while. Individual beetles can live for 30 to 45 days. Because the beetles emerge from the soil over time, populations of Japanese beetles will be present in any given area for several weeks, well into August. The beetles are particularly active and noticeable on hot, sunny days, and they tend to keep a low profile when the weather is cloudy and cooler.
As we have discussed in several previous articles, the primary threat posed by Japanese beetles right now is their potential for interfering with corn pollination by clipping silks. In fields that have not begun to tassel, large numbers of Japanese beetles are scraping the green tissue from corn leaves. The injury is similar in appearance to the leaf-feeding caused by western corn rootworm adults. (Refer to the article about western corn rootworm adults in this issue of the Bulletin.) However, unless leaf-feeding injury is excessive, yield should not be compromised, so we urge people to wait to see if Japanese beetles start clipping silks before applying an insecticide. If an insecticide is applied too early, a second application may be necessary if Japanese beetles reinfest the field.--Kevin Steffey