Japanese beetle

Michael R. Bush, Christopher Adams, and Sven Spichiger
Revised: 
March 2021

The Departments of Agriculture in Oregon and Washington State have trapped adult Japanese beetles (Popillia japonica) for over 30 years. Isolated infestations of this beetle were eradicated in the past. In 2016, hundreds of adults trapped near Portland initiated another eradication response effort. Quarantine areas are in place and this eradication program will continue through 2021. Multiple findings of Japanese beetles were detected in Washington State, and efforts are in play to eradicate these beetle populations.

Pest description and damage The adult beetle is a colorful flower beetle with iridescent copper-colored wings and a metallic green thorax with a series of tufts of white hair along the perimeter of the abdomen. The adult measures about 0.375 of an inch long. In the summer months, these adults congregate and skeletonize the leaves of a wide range of ornamental plants including roses, phlox, mallow, asters, maples, oaks, willows, lindens and rhododendrons, as well as crops including peaches, cane berries, grapes, hops, potatoes and tomatoes. In late summer, these adults mate and lay eggs in the soil beneath host plants. The mature larvae are C-shaped white grubs that tunnel under the ground surface, feed on the roots of grasses and can be found in lawns during the spring. Japanese beetle larvae are serious turf pests in eastern North America. The Japanese beetle overwinters as larvae in the soil and pupates in soil chambers in the spring. There is one generation each season. Nevertheless, this insect is capable of building up a large population in a short period.

Pest monitoring Traps that rely on an aggregation pheromone and/or a floral lure to attract and monitor both male and female beetles are commercially available. WSDA traps for Japanese beetle every year. Most Japanese beetle detections are associated with air cargo.

Management This is a quarantined pest species. If you suspect you have found plant damage, turf damage, the C-shaped larvae or the adult beetle, do not hesitate to report the finding to the State Department of Agriculture or local university Extension office. For the larvae, a trained specialist looking at the physical sample under a microscope must do species identification (physical specimen required). When confirmed as a Japanese beetle, these state agencies will respond and work to eradicate this pest as soon as possible. Several pesticide products, both organic and conventional, that target the adult and the larval stages of the Japanese beetle are available.

For further information:

Suits, R., H. Stoven, G. Langellotto-Rhodaback & C. Burfitt. 2017. Japanese Beetles in Oregon.

https://catalog.extension.oregonstate.edu/em9158