Japanese beetle (Popilia japonica) has been established in the eastern United States since the early 1900s. Slow the Spread (STS) efforts coordinated by state and federal agencies have helped to keep several western states, including Washington and Oregon, free from Japanese beetle. The Departments of Agriculture in Oregon and Washington have surveyed adult Japanese beetle 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. Multiple finds of Japanese beetle were detected in Washington, 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 inch long. In the summer months, these adults congregate and skeletonize the leaves of a wide range of ornamental plants including rose, phlox, mallow, aster, maple, oak, willow, linden, and rhododendron, as well as crops including peach, caneberry, grape, hop, potato, and tomato. 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 Japanese beetles 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, report the finding to your state Department of Agriculture or local university 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 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