Stink bug

YAKIMA — An increase in brown marmorated stink bugs has scientists concerned the Asian pest could threaten tree fruit and other crops in Eastern Washington next year.

In recent weeks, researchers have captured hundreds of the bugs in traps, mostly in Yakima and Walla Walla. One pheromone-baited trap outside a Yakima residence collected nearly 200 bugs in five days, said Michael Bush, Washington State University Extension entomologist.

“That compares to 36 we captured for all of 2015 throughout Yakima County, so it’s quite a jump,” he said.

WSU Extension agents and master gardeners are getting more calls from people finding the bugs in their homes and offices as they escape the fall chill, he said.

The bugs are so named because they emit a smell of dirty socks when crushed.

Called “the Beast of the East,” it was identified in Pennsylvania in 1996 and caused an estimated 30 percent loss in apple and peach crops in the mid-Atlantic states in 2010.

Growers there resorted to broad-spectrum synthetic pyrethroid pesticides to control the bugs at the expense of their integrated pest management programs, said Elizabeth Beers, entomologist at the WSU Tree Fruit Research and Extension Center in Wenatchee. She’s on a national team of scientists fighting it.

The bugs were found in Portland in 2004 and later in the Willamette Valley, Medford, Hood River and Vancouver. In 2012, traps first caught two bugs in Yakima.

The insect has more than 300 host plants and spreads by human movement.

Beers said it’s natural for the bugs to increase but that they seem to like moist climates such as Portland’s and Vancouver’s. Nonetheless, they are well established in Yakima and Walla Walla and have been found in Wenatchee.

“I am very concerned,” Beers said. “I work with tree fruit and it’s considered one of the highest, at-risk crops. I’m not sure why.

It eats lots of things and apples are very prone to attack.”

Peaches, nectarines and pears are probably more vulnerable than cherries, she said.

Broad-spectrum pyrethroid pesticides are an option in the event of a large outbreak, but growers could also sacrifice a tree by baiting bugs there and spraying it, Beers said.

Netting already used for weather protection is an option, and so is biological control, she said.

Over a year ago, an Asian wasp, Trissolcus japonicus, which eats brown marmorated stink bug eggs, was found in Vancouver and is better able to combat the bugs than native egg parasitoids, Beers said.

“It’s probably not a silver bullet, but it may help keep populations down to a dull roar,” she said. “It could help prevent an explosion but won’t eradicate it.”