2008 Year in Review

From the Fields

Japanese beetles have been reported in some corn and soybean fields in northern Illinois. They have intensely infested certain fields in the southern two-thirds of the state. Producers should be on alert for this insect pest.

As its’ name implies, the insect is native to Japan and was first introduced into the United States in 1916. The host range of this insect is very large. Adult Japanese beetles will feed on over 300 species of plants, including some field crops, ornamental plants, shrubs, and garden plants. The worm stage (larva) feeds on roots of many turfgrasses, field crops, ornamental plants, and vegetables.

The adult beetle is about one-half inch in length and is metallic green with bronze-colored wing covers. There is one generation per year. The insect overwinters as a larvae and the adult beetle lives for 30 to 45 days. Japanese beetles are naturally gregarious and tend to aggregate on host plants. The beetles are attracted to flowering plants, so they will also be found on flowering weeds.

In corn, adult Japanese beetles feed on silks, interfering with the pollination process. Extensive silk clipping may lead to incomplete ear fill and yield loss. To protect pollination from silk clipping by Japanese beetles, an insecticide application may be warranted when there are three or more beetles per ear, pollination is not complete, and silk clipping is observed.

In soybean, Japanese beetles are one of several insects that can defoliate plants. Insecticidal treatments should be considered when defoliation reaches 30 percent before bloom and 20 percent between bloom and pod fill.

These economic thresholds for corn and soybean have been in place for many years, and it is difficult to know what specific changes are necessary for modern hybrids and varieties, higher yield expectations, and current commodity prices. Experience and good judgment need to be utilized when making treatment decisions.

However, application of an insecticide to prevent infestation of Japanese beetles is not warranted. Various insecticides are suggested for control of Japanese beetle in corn and soybean. Consult the 2008 Illinois Agricultural Pest Management Handbook, available at University of Illinois Extension offices and on-line at IPM. Be sure to read and follow label directions and precautions. A fact sheet on Japanese beetles can be found at this University of Illinois web site.

by  Editor, theCity1.com
July 29, 2008