Stink bug numbers ‘explode’ along East Coast

November 15th, 2010
This summer as the first, major population explosion of a new, invasive insect hit the middle Atlantic region, researchers at the U.S. Department of Agriculture were busily trying to find a natural enemy to fight it.

The sudden blossoming of brown marmorated stink bug numbers signaled the arrival of a major agricultural pest and a minor but aggravating household one.

Newly-arrived alien insects often survive under the radar for years before their population suddenly reaches a point where they “explode,” says Douglas Luster, research leader at USDA’s Beneficial Insects Introduction Research Unit in Newark, Del. This variety of stink bug is originally from Asia and was first seen in the United States in 1998 in Pennsylvania. It’s now been detected in New Jersey, Maryland, Delaware, West Virginia, and Virginia. Limited populations also have been detected in Mississippi, Ohio, Oregon, and California, according to USDA.

The stinkbugs got their name for the herbal, pungent smell they emit when frightened. This summer there was a major infestation of the brown, three-quarter-inch bugs in houses across the mid-Atlantic.

“We had three or four nights in a row when we had hundreds of them in our bedroom,” says Luster. The bugs don’t bite and can’t fly well, so while a nuisance they’re not dangerous to humans. “They vacuum up pretty well,” he says.

But while annoying in the home, in the field they are becoming a major agricultural pest. The bugs suck the juice out of corn, fruits and other crops, making them unsalable. Back in 2005 USDA researcher Kim Hoelmer began looking to see if the brown marmorated stink bug had any natural enemies in the United States. Although he discovered a native parasitic wasp that laid its eggs in stink bug egg masses, it only infected about 5% of them, not enough to knock back the invading species.

To find a better biological control, Hoelmer went to Asia where he discovered three species of tiny Asian parasitic wasps that lay their eggs inside stink bug eggs, destroying them. The Asian wasps showed rates of parasitism as high as 50% to 80%.

The team is now studying these wasps in USDA’s high-security containment facility in Newark, to ensure that they do not pose a threat to native American insects.

Introducing a non-native species to go after another non-native species is a delicate operation because of the possible unintended consequences. In 1930 poisonous South American cane toads were introduced into northeast Australia to attack sugarcane beetles, but ended up being a major pest on their own.


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