Insects
6:35 am
Fri December 6, 2013

Stink Bug Spread Alarms Growers, Scientists

A malodorous invasive bug has gone from a worry to a certifiable nuisance for some Northwest (or Western) farmers and gardeners. The name of this insect is a mouthful: the brown marmorated stink bug. Researchers say the population really seems to have taken off this year. With the approach of winter, these stink bugs are leaving the fields and may just crawl into your home.

Invasive stink bug on an olive branch in the Willamette Valley
Invasive stink bug on an olive branch in the Willamette Valley
Credit Tom Banse

One of the ways scientists are following the spread of the non-native stink bug is by setting traps. There are four traps at the edge of this blueberry field at Oregon State University's North Willamette research farm.

Scene: (opening traps): "Looks as if we have at least three in this one..."

OSU entomologist Vaughn Walton is looking for a brown bug with a body in the shape of medieval shield and distinctive white stripes on its antennae. It's about the size of the fingernail on your ring finger. It's called a stink bug for good reason.

Vaughn Walton: "This looks like a live one over here. He is alive! Let's give you an opportunity to smell a brown marmorated stink bug..."
TB (sarcastically): "Oh, thank you very much." (laughter)
[faint sniff, sniff]
TB: It's a slight aroma. It's a little bit like sweaty socks, I guess.
Vaughn Walton: "Many people say it's like a cilantro flavor. Some of the people in my lab used to like cilantro. Now they hate cilantro."

Here's why this bug invasion raises alarms. A stink bug can transmit that flavor into berries and fruit when it feeds. It can hide in wine grape clusters and then taint the juice when the grapes are crushed. Early season attacks cause shriveling of berries and nuts. On vegetables, stink bug bites cause blemishes.

Vaughn Walton: "I'd say this year it started to become way more alarming than last year because we are finding it in commercial crops. We didn't see them as easily in commercial crops last year. I think one of the main reasons is that this season was really perfect for them to multiply. We're looking at at least two generations this year."

The brown marmorated stink bug is 1-2 centimeters in length
The brown marmorated stink bug is 1-2 centimeters in length
Credit Tom Banse

There are native stink bugs in the Northwest, which farmers typically don't worry about. This more voracious variety comes from East Asia. Scientists detected it for the first time in the American Northwest in Portland in 2004. Walton says the bug has spread south to Ashland, north into Washington and east up the Columbia River Gorge through to Walla Walla.

Vaughn Walton: "They are really good hitchhikers. They move on cars, on cargo, on trains and stuff like that."

Washington State Department of Agriculture managing entomologist Jim Mara says he's getting reports of crop damage for the first time this year. His counterpart in Idaho reported the state's first detection of the invasive stink bug in Nampa last year.
Back in the Willamette Valley, Michelle Armstrong and her fiancé grow sweet corn and vegetables in the vicinity of Brooks.

Michelle Armstrong: "Hopefully we'll learn how to control this pest. We definitely see it as a major threat."

Numerous universities are looking into control measures using U.S. Dept. of Agriculture funding. Armstrong has discussed the matter with many surrounding farmers by virtue of her other job as a sales consultant for the ag supply company Wilbur-Ellis. She says nothing has come on the market yet that specifically targets this insect.

 OSU entomologist Vaughn Walton and Wilbur-Ellis agronomist Michelle Armstrong check a trap for stink bugs near Aurora, Ore.
OSU entomologist Vaughn Walton and Wilbur-Ellis agronomist Michelle Armstrong check a trap for stink bugs near Aurora, Ore.
Credit Tom Banse

Michelle Armstrong: "That's part of the worries for the growers. As a grower myself, what will I do when this pest gets in my field? I don't have a lot of options. We don't want to spray more than we have to."

Now that we've come to the end of the growing season, the invasive stink bugs are looking for comfy places to hibernate. They could crawl into your home given the opportunity. Researchers want to hear from you if you find brown marmorated stink bugs. There's a web page with identification tips and a form to report sightings at: http://www.stopbmsb.org/