Japanese Beetles Reported for First Time in Nebraska Field Crops - UNL CropWatch, July 19, 2011

Japanese Beetles Reported for First Time in Nebraska Field Crops - UNL CropWatch, July 19, 2011

July 19, 2011


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Japanese beetle

Japanese beetle in a soybean field south of Crete.  (Photos by Randy Pryor)

Japanese beetle damage to soybean

Japanese beetle damage to soybean plants.

UNL Extension Educator Randy Pryor visited a soybean field in response to a grower call, and found Japanese beetle (Popillia japonica) adults feeding on soybean foliage in a field south of Crete. Japanese beetles are a common pest of corn and soybeans in the eastern Corn Belt, but we have not received previous reports of injury in Nebraska corn or soybeans.

We have had Japanese beetles in several urban areas of eastern Nebraska over the last 20 years, including current infestations in parts of Omaha and Lincoln. Japanese beetles were reported previously in 1994 on turf in Crete at the Country Club.

Description and Life Cycle

Japanese beetles are an annual white grub species, with a life cycle similar to the masked chafer beetle, which is a common pest of turf in Nebraska. Japanese beetle adults are about 1/3 to 1/2 inch long and about 1/4 inch wide. Adult beetles have a metallic green thorax and head and copper brown wing covers which do not cover the tip of the abdomen. On each side of the abdomen are five tufts of white hair, with an additional pair of white tufts on the top of the last abdominal segment.

Unlike the masked chafer beetle, the adult Japanese beetle is a voracious feeder of flowers and foliage of numerous plant species. Adults scrape away the surface leaf tissue, leaving the veins and mid-ribs intact, producing a skeletonized appearance. Beetles are attracted to feed on previously damaged plants so they are often concentrated in hot spots within a field, severely damaging individual plants. On corn Japanese beetles are often found feeding on silk in the ear tips.

Japanese beetles lay eggs in the soil. These eggs hatch out in the summer and begin feeding. The larvae are similar in appearance to the white grubs we typically see in turf. Grubs go through three instars during the summer and overwinter as last stage larvae in the soil. They pupate in the following spring and emerge as adults in the summer.

Thresholds and Treatment

In soybeans, during the reproductive growth stages, if insects are present and defoliation is expected to exceed 20%, treatment is recommended. In corn, University of Missouri entomologists suggest treatment if three or more Japanese beetles per ear are present during silking and pollination is not complete.

A variety of insecticides are effective in controlling adults, including pyrethroid insecticides and products containing carbaryl.

Bob Wright
Extension Entomologist