The Japanese beetle (Popillia japonica) has been established in the eastern United States since the early 1900’s. Efforts to slow the spread by the USDA have helped to minimize the presence of Japanese beetle in the Pacific Northwest. The Departments of Agriculture in both Oregon and Washington have surveyed for adult Japanese beetles for over 30 years. Isolated infestations of this beetle have been eradicated in the past. In 2016, hundreds of adult beetles trapped near Portland initiated another eradication response effort. Quarantine areas are in place and this eradication program will continue. Multiple sightings of Japanese beetles have occurred in Washington, and efforts are currently 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 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, 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. 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 can build up large populations in a short period of time.
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 turf damage, the C-shaped larvae, or the adult beetle, do not hesitate to report the finding to the State Department of Agriculture or your local Extension office. For the larvae, a trained specialist looking at a 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