Scientific name: Popillia japonica

What Is It?

The Japanese beetle is a garden pest native to northern Japan. The adults eat the leaves of plants while the larvae attack the roots, particularly the roots of grasses.

Is It Here Yet?

No, but it is established in the eastern United States. Japanese beetles also are constantly transported into the Pacific Northwest on cargo planes, trucks, and in household goods. Despite this, they haven’t yet become established in Washington. Infestations have occurred in Idaho and Oregon, and both states have implemented costly eradication programs in response.

Why Should I Care?

Japanese beetles attack hundreds of different species of plants, including native species and popular gardening and landscaping plants. An infestation can cause severe damage to plant leaves, and plants that were stressed before an infestation may not survive.

How Can We Stop It?

Making sure you’re not transporting the adults or grubs in plants or soil. Though the adults can disperse by flying, transportation by humans is their fastest way of invading new areas.

What Are Its Characteristics?

  • Adults are metallic green and copper, about 3/8 inch long, with a classic “scarab” beetle shape.
  • Adults have several small white fuzzy spots along the edge of their abdomens below each wing.
  • Larvae are nondescript white grubs found in the soil, and look very much like many native and other exotic species. Grubs are best identified by an experienced entomologist.

How Do I Distinguish It From Native Species?

There are a few species of green adult scarabs that look like Japanese beetle, and many kinds of grubs. If you have a suspect beetle please submit it to the Washington State Department of Agriculture.

Identification photos courtesy of the U.S. Department of Agriculture Animal and Plant Health Inspection Service. Page header image courtesy of Joshua Dunlap, Oregon Department of Agriculture.