They don't make fruit and vegetables inedible as some insects do, but stink bugs can turn a beauty of an apple or berry or ear of corn into a beast destined for food processing.
Best known to annoyed homeowners, stink bugs are a substantial agricultural pest that farmers and researchers have not fully figured out how to eliminate.
"They really seem to enjoy the orchards. They seem to enjoy pretty much any fruit or vegetable," said Rob Shenot, owner of Shenot Farm & Market in Franklin Park and president of the Pennsylvania Vegetable Growers Association.
"We lost almost 80 percent of certain varieties of apples. Stink bugs put them into the juice bin. It takes it out of the Grade A apple category," said Reed Soergel, whose family owns Soergel Orchards in Franklin Park.
Stink bugs arrived in Western Pennsylvania in large numbers about four years ago.
They've become the biggest fruit and vegetable pest since the coddling moth in the 1970s, Soergel said. Stink bugs are even more persistent, he said.
"You can spray all you want, but they'll be back the next day," he said.
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The bugs are found in 41 states.
"They are a challenging insect," said Tracy Leskey, an entomologist with the U.S. Department of Agriculture.
Stink bugs do not make fruit inedible or infect it. They do, however, substantially lower the value of a crop — as much as 90 percent — by disfiguring it, agricultural experts say.
"Fruit loses visual appeal. Stink bugs destroy the looks of the crop. Apples that might sell for $1.50 per pound at a farmers market or grocery store will be sold for processing at one-tenth of that price if they are disfigured by stink bugs," said Greg Krawczyk, a tree fruit entomologist at Penn State's Fruit Research and Extension Center in Biglerville, Adams County.
Adams County produces half of the apples in Pennsylvania, which is the nation's fourth-largest apple producing state.
In just the Mid-Atlantic region — which includes Pennsylvania, Delaware, New Jersey and New York, the nation's second-biggest apple-producing state — apple growers lost $37 million to the bug in 2010, according to the USDA.
"The damage to fruit can resemble what an orchard looks like after a hail storm. The bugs leave a nasty corking spot on the fruit," Shenot said.
The pests have started to disfigure grapes in Oregon's Willamette Valley, a wine region, and in Washington state, which produces two-thirds of the country's apples.
With a mix of traps and insecticides, Shenot and other growers have had some success in thwarting the spread of the pesky insects. If a trap is full of stink bugs, growers know whether to treat their crops.
The pest's appetite is not limited to apples. Stink bugs feed on raspberries and blackberries, corn, tomatoes, peppers and beans.
Stink bugs have a shell that's about a quarter of an inch long. When crushed or trapped, they emit a smell many compare to old socks or rotting cilantro.
"We are still working on what to do about them," Shenot said.
This year's population is lower than in previous years but is high enough to be a concern and turning out to be higher than what researchers expected after a cool summer, according to Krawczyk.
Stink bugs originated in Asia and were first identified in the United States in Allentown, Lehigh County, in 1998. They were likely in the country for years before that, Krawczyk said.
"We have not seen them on conifers. They are on just about anything else," he said. In summer, they are nearly invisible to most people. "They are not around houses. They are in soybean fields and orchards," Krawczyk said.
That changes as soon as weather gets colder, especially after the first hard frost, as stink bugs work their way into warmer places indoors.
The migration sometimes terrifies homeowners, Krawczyk said. Two years ago, a Maryland home had a buildup of 26,000 stinkbugs after winter.
