The Japanese beetle is becoming an increasingly prevalent pest in the north-central region of the United States and can occasionally be an economic problem in soybean or corn fields, says Kelley J. Tilmon, South Dakota State University Extension soybean entomologist. For clarification purposes, Tilmon wants to ensure that readers do not confuse the Japanese beetle with the Asian ladybeetle, which is often called Japanese beetle by mistake.

"Asian ladybeetles are familiar to many as the yellow or orange ladybeetles that come into houses in the fall and are beneficial predators of crop pests," she says.

Japanese beetles are large – up to a half inch long – and metallic green and copper colored. Adults feed on the leaves and flowers of more than 300 plant species. They are an introduced pest first found in the United States in 1916 in New Jersey.

"Only in recent years have they become common in the Midwest," Tilmon says.

 

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The South Dakota Department of Agriculture monitors for this pest with traps, and it has been detected in several South Dakota counties particularly in the southeastern part of the state.

Life cycle of the Japanese beetle

Japanese beetle immatures are soil-dwelling white grubs that feed on roots and organic material and are often pests of turfgrass. The adults typically feed between the veins of leaves causing a characteristic lacy or "skeletonized" damage. They feed on a wide range of plants including various ornamentals, fruits and vegetables.

Though they are more common in horticultural settings, they will also feed in field crops, including corn and soybeans. In soybean fields they cause defoliation of leaves, which reduces photosynthesis, and in corn they feed on silks, reducing kernel set.