Japanese Beetle Eradication in Portland - Progress and Challenges

The Japanese beetle (Popillia japonica) is a polyphagous invasive insect pest that threatens Oregon and the western United States. It has been established in the eastern US since the 1916, and has caused billions in damage to eastern US agriculture. Japanese beetle feeds on over 300 plant species, including roses, grapes, and blueberries. Adult feeding damage skeletonizes leaves, defoliating the plant while larval feeding damages grass roots. Repeated or severe feeding kills host plants. The largest Japanese beetle population detected in Oregon was discovered in 2016 in Cedar Mill, Bonny Slope, Oak Hills, and Bethany neighborhoods. Oregon department of agriculture began an eradication and trapping program. Most properties were treated with a single application of the granular larvicide Acelepryn® G (Chlorantraniliprole) on lawns and ornamental planting beds. The 2024 season granular treatment area included approximately 1,300 acres, down from a peak of 4,200 acres in 2021. Successful eradication of several small pockets of beetles allowed the treatment area to be almost half the size it was in 2023. In 2024, ODA placed 10,272 traps throughout the state in all 36 counties. Japanese beetle traps are an extremely effective monitoring tool. Our trapping effort showed that we continue to reduce the total beetle population across the treatment area. One property repeatedly refused treatment, which led to a population spike in 2023. We have since treated that property. With time and funding, we believe we can eradicate Japanese beetle, but the future of the program is uncertain at this time.