Japanese Beetles Habitat

Natural Range

• As its name suggests, the Japanese beetle is native to Japan, where it is not considered an invasive pest. It prefers large, grassy areas for development and reproduction, both of which are not readily available in that country. Native predators, parasites and diseases also help keep Japanese beetles under control in its native range.

Introduced Range

• The Japanese beetle is a serious invasive pest in the United States. According to the California Department of Food and Agriculture, these beetles were accidentally introduced via plants in a New Jersey nursery in 1916. The beetle has slowly spread westward, and is found from Maine to Alabama. Small infestations of the Japanese beetle have appeared west of the Mississippi River. The Japanese beetle has also appeared in some other states, such as California, but has been successfully eradicated.

Host Plants

• According to the University of Ohio, Japanese beetles are herbivorous. Adults eat leaf tissue, but not leaf veins, leaving behind a lacy-looking leaf skeleton. These leaves soon die. Japanese beetles have been known to feed on over 400 species of broad-leaved plants, but prefer about 50 species, including grape, fruit trees, rose and zinnia, corn silk and alfalfa. Japanese beetle grubs feed on the roots of plants, including shrubs and ornamental trees, lawn grasses and garden crops.

Life Cycle

• Japanese beetles normally have only one generation per year, but wet soils may cause the grubs to require up to two years for development. In most cases, the larvae pupate in June, and adults emerge in late June and early July. They begin to feed as soon as possible, and soon mate. After a day or two of feeding, females burrow into the soil, laying eggs two to four inches below the surface. They repeat this process several times. Grubs hatch between 10 to 30 days, and begin eating plant roots from tunnels below the soil's surface.

Control

• Japanese beetle control is difficult, but altering their habitat can help reduce their population. Growers can avoid irrigation while the eggs and larvae are developing, especially in areas with low natural rainfall. It's also possible to avoid planting preferred species near the kind of soil Japanese beetles prefer for laying. Red and silver maples, dogwood, cedar, lilac and other species are more resistant to these pests.