Stink bugs, the smelly scourge of the mid-Atlantic, are hitch-hiking and gliding their way across the country. Officially known as the brown marmorated stink bug, sightings of the pest have been reported in 33 states, an increase of eight states since last fall.
“I would say people now regard them as an out-of-control pest,” says Kim Hoelmer, a research entomologist at the U.S. Department of Agriculture in Newark, Del.
The National Pest Management Association warns homeowners this week that the bugs’ growing populations are likely to make infestations significantly worse this year. “This season’s stink bug population will be larger than in the past,” says Jim Fredericks, director of technical services for NPMA.
The bugs have been spotted as far west as California, as far north as Minnesota and as far south as Florida. Only the Rockies and Plains states have escaped thus far. The eight states recently joining the stink bug party are Arizona, Iowa, Georgia, Michigan, Minnesota, Vermont, Washington and Wisconsin, according to the USDA’s Greg Rosenthal.
Rosenthal says a report of a stink bug in a state does not necessarily mean that the pest is established or that agricultural damage has been reported in that state.
Stink bugs are named for the pungent smell they emit when frightened, disturbed or squashed. “They have glands that produce a defensive compound, which has a strong odor that repels predators,” Hoelmer says. “It makes them particularly obnoxious.”
Entomologist David Rider of North Dakota State University says there are more than 4,700 species of stink bugs in the world — 250 of them in the USA and Canada. Some of these are agricultural pests, while others are beneficial predators that feed on insects — but now it’s just the brown marmorated one in the USA that’s causing all the fuss.
Last summer, there was a major infestation of the brown, three-quarter-inch bugs in homes throughout the mid-Atlantic, the worst reports coming from West Virginia, Virginia, Delaware, Maryland, Pennsylvania, and New Jersey.
“In this area, people are literally finding thousands in their homes,” reports Tracy Leskey, a research entomologist with the USDA in Kearneysville, W.Va.
They’re just a stinky nuisance for many, but the bugs can be devastating to farmers.
“They feed on a wide range of important food crops,” Hoelmer says. Crops such as sweet corn, apples, pears, grapes, berries, peaches, tomatoes and peppers appear to be the most vulnerable.
“Some growers have lost their entire crop to stink bug infestations,” Hoelmer says. “This adds up to many millions of dollars of losses in crop values. It’s a serious economic loss to some growers.”
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USDA officials “take this pest seriously and are hard at work trying to understand effective ways to control it and mitigate its effect,” USDA spokeswoman Jennifer Martin says.
Two USDA agencies — the National Institute of Food and Agriculture and the Agricultural Research Service — fund projects at universities and research centers to study how to control and combat stink bugs.
Funding for the USDA’s stink bug research in fiscal year 2010 totals nearly $1.09 million, Martin says.
The two seasons when people most notice the bugs are in the fall — when they come inside homes looking for warmth and shelter — and in the spring, when they look for ways to come out of hiding.
For farmers, the entire growing season is the time to be wary.
Most people aren’t bothered. The bugs don’t bite and aren’t poisonous. “They don’t transmit disease and don’t suck blood,” Leskey says.
However, “they are great at hitchhiking” she says, preferring to hide in people’s personal belongings and in cars.
The bugs probably got to the USA in the late 1990s by hitchhiking in container ships from Asia.
Another way they get around is when they’re picked up by the wind. “They have wings and can fly far,” Leskey says.
“The wild population is increasing and moving from state to state” Hoelmer says.
First positively identified in the USA in the late 1990s in Allentown, Pa., the Asian bugs have few natural predators in the USA. “Native species do not seem to recognize them as prey,” Hoelmer says.
However, a tiny parasitic wasp from Asia known as a Trissolcus wasp — a bug smaller than a gnat — is showing promise as a possible biological control. These wasps, which are natural enemies of the brown marmorated stink bug in Asia, might be able to nip the stink bug explosion in the bud by preying on brown marmorated stink bug eggs, the only type of eggs that species of wasps eats.
Hoelmer says that research is underway to determine whether it will be safe to release this specific species of wasp into the wild in the USA: “We already know that each species of Trissolcus only recognizes certain kinds of stink bugs as suitable food for their offspring. If they cannot locate ‘their’ species of stink bug hosts, they won’t reproduce and they won’t survive.
However, we want to be sure that any wasps that are released to control the brown marmorated stink bug will not create problems for other stink bugs, especially species that are beneficial.”