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Japanese Beetle - The Bug Review - University of Illinois Extension

Japanese Beetle

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Japanese beetles feeding

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Japanese beetle on rose

The adult is a colorful beetle 1/3 - 1/2 inch long with a shiny metallic green color and coppery brown wing covers. There is a row of five tufts of white hair along each side of the abdomen and two additional tufts on the top of the abdomen tip.

The larvae are white grubs that take on a grayish cast from the accumulation of soil and fecal matter in the hindgut. They have a characteristic "C"-shaped form, grow to about one inch long, and may be separated from other turfgrass feeding grubs by their characteristic "V"-shaped pattern of spines on the underside tip of the abdomen. The bottom of the V points toward the head and may be seen with a hand lens.

Habit

The Japanese beetle has a one year life cycle, spending about 10 months as a grub in the soil. In late June, the first adults emerge with most present in July and August. Some may still be found in early September. Throughout the summer, adult beetles feed on a wide range of plants and deposit eggs in the soil. Eggs hatch about two weeks later and grubs feed on decaying matter and roots until temperatures cool in the fall. They move downward and overwinter as a partially grown grub and resume some feeding activity in spring. Pupation occurs in late spring and adults begin emerging in late June.

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Japanse beetle damage on linden

Damage

Japanese beetles are chewing insects that destroy leaves, flowers and fruits of more than 276 plants. These beetles can completely skeletonize leaves, feed on corn silk and corn ear tips and are especially destructive to grapes, peaches and other members of the rose family. The grubs feed on grass roots in lawns, parks, golf courses, and cemeteries.

Control

Non-chemical: For adults, hand-picking can reduce population numbers. The use of traps may attract more beetles and therefore is not recommended. Selecting plants that are less preferred may be helpful.

For grubs, the bacterium, Bacillus popilliae,sold as milky spore disease, must be applied to the soil and usually takes several years for it to build up to levels that are effective against the grub. Milky spore disease is ineffective against the annual white grub, that is usually found with Japanese beetle grub populations in Illinois. Annual white grub is the most serious turfgrass grub in Illinois.

Chemical: Contact your county Extension office for current pesticide controls.