OSU releases guide about invasive Japanese beetles

May 8, 2017
A five-year eradication program targets Japanese beetles. Photo by Oregon Department of Agriculture.
A five-year eradication program targets Japanese beetles. Photo by Oregon Department of Agriculture.

CORVALLIS, Ore. – Japanese beetles, a voracious invasive pest that feeds on more than 300 plants, were found in record-breaking numbers in areas of Portland in 2016.

In response to the growing infestation, the Oregon State University Extension Service developed a guide about the destructive insect. Japanese Beetles in Oregon was co-authored by Rachel Suits, an Extension entomologist, who said the bright metallic green beetle has a particular preference for turf and roses.

“Larvae feed on grass roots and adults have mandibles to chew on leaves and flowers of about 300 plants,” she said. “They specifically love roses, which could be devastating to the City of Roses.”

First detected in New Jersey in 1916, Japanese beetles became firmly entrenched as the use of lawns grew in the 1950s and ‘60s and are now a major pest throughout the eastern, southeastern and midwestern states. It hitched a ride to Oregon on air cargo carriers and was found at the Portland International Airport in 2000 and every year since.

Last year, 369 beetles were trapped by the Oregon Department of Agriculture in northwest Portland, specifically in the Cedar Mill and Bonny Slope areas. More were found feeding on roses and other plants in these largely residential areas. In response, the ODA started an eradication effort that includes applying a pesticide called Acelepryn on lawns and beds in the affected communities. It is applied to the ground; no spraying or aerial application will be done.

“This area of northwest Portland could be considered a high-risk area for the introduction of Japanese beetle because a number of people have moved into the neighborhoods over the last five years,” said Clint Burfitt, manager of ODA’s Insect Pest and Prevention and Management Program. “I suspect somebody might have brought this in on house plants.”

The impact to all crops, commodities and other related businesses could be as high as $45.5 million if Japanese beetles become established in Oregon, according to an ODA risk analysis. The environmental impact could be equally significant, said Burfitt, a consultant on the OSU Extension publication.

“Because pesticides would have to be applied annually, in perpetuity, to keep plants like roses or other ornamentals alive – or in the case of growers of wine grapes, hops or in particular horticultural plants – the establishment of Japanese beetle would result in ongoing pesticide use,” he said. “In a high Japanese beetle population, people have a hard time growing many of the plants they prefer to grow in an urban setting.”

Suits described the greedy adult Japanese beetles, which emerge in the beginning of summer, as having tannish red, hardened forewings, green coloring on the shoulder area and white tufts along the edge of the abdomen. Unlike the root-feeding larvae, the adults ravage foliage and flowers, leaving skeleton-like leaves and petals behind that no longer have the ability to photosynthesize.

Experts don’t recommend that homeowners use products to control beetles on their property at this time. However, residents are asked to keep an eye out and report sightings to 1-866-INVADER or on the Oregon Invasive Species Online Hotline. Refer to the Extension's Japanese Beetles in Oregon for photos of the beetle. If you’re unsure if it’s a Japanese beetle, you can take it to your local Extension office for identification.

Author: Kym Pokorny
Source: Rachel Suits