I've heard there are Japanese beetles lurking in the Illinois Valley. Does that pose a threat to the vineyards?

I've heard there are Japanese beetles lurking in the Illinois Valley. Does that pose a threat to the vineyards?

— Travis J., via email

Yes, those pesky critters, which first surfaced in Josephine County a decade ago, are back.

Oregon Agriculture Department entomologist Barry Bai tells us that this round of Japanese beetles began showing up in traps during 2010, arriving from Cedar Rapids, Iowa.

"During the process we came across a family who had just moved from Cedar Rapids, and they told us Japanese beetles had been a big problem there," Bai said. "The eggs were laid in a potted plant they brought with them."

In 2010, five beetles showed up in traps, even after extensive ground treatment, Bai said; 14 showed up last year.

Grubs, found mostly in the soil, aren't too mobile and prefer eating the grass roots in lush lawns or golf courses. Adult Japanese beetles take to the air and are known to feed on 250 plant species. Their favorite foods include roses, linden ornamental trees, fruit trees and, just as you suspected, grape vines.

In 2010, it was too late to treat the grubs. But even after turning up the heat in 2011, more adults were found.

"We'll go back and try to get rid of them," Bai said. "They're still concentrated in a small area, a couple of street blocks — about 30 acres or so."

The ground treatment begins in May followed by foliage spray in July and August.

Send questions to "Since You Asked," Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by email to youasked@mailtribune.com.