WENATCHEE, Wash. — Scientists hope the discovery of the spread of a natural predator may help control the brown marmorated stink bug.
Trissoicus japonicus, a non-stinging Asian wasp, was found Aug. 14 and again Sept. 23 in a trap in a public park in Vancouver, Wash.
The trap was part of an effort by the Washington State University Tree Fruit Research and Extension Center in Wenatchee to find natural combatants to the brown marmorated stink bug.
Josh Milnes, a field technician in Vancouver for the center, found two small clusters of the wasps. They were verified by USDA research entomologist Elijah Talamas in Washington, D.C., said Elizabeth Beers, WSUTFREC entomologist in Wenatchee and Milnes’ supervisor.
Beers is part of a nationwide team of 52 scientists from 10 institutions working to control the stink bug.
“We did not expect to find this wasp here and are very excited. In the insect world, we struck it rich,” Beers said.
Since 2007, USDA has been studying T. japonicus in quarantine laboratories to determine if it can be released to destroy the brown marmorated stink bug, also from Asia, without harming native stink bug species beneficial to crops.
Tracy Leskey, USDA entomologist in West Virginia and leader of the national stink bug team, said the discovery may be a biological-control game-changer.
T. japonicus wasps clusters have been found in Maryland and Virginia in the past two years and the fact that they’ve shown up 3,000 miles away in Washington state shows the wasp is deploying for attack, Leskey said.
The discovery also suggests the wasp was accidentally brought to the United States multiple times, much like the stink bug, she said.
The stink bug has caused millions of dollars in damage to fruit orchards in the Mid-Atlantic region since it was discovered in Pennsylvania less than two decades ago. It was discovered in Portland, Ore., in 2004 and is becoming a problem in berries, vineyards and other crops in the Willamette Valley.
It was found in Yakima, Wash., in 2012 and is feared for its potential destruction of apples, pears and cherries.
WSU scientists have been alarmed because only broad-spectrum pesticides have worked against the stink bug. Those pesticides also disrupt Integrated Pest Management programs of biological control.
The T. japonicus wasps found by Milnes were destroying brown marmorated stink bug eggs, Beers said.
The female T. japonicus wasps, no bigger than a typed comma, lay eggs inside clusters of stink bug eggs. After a wasp egg hatches, the larva eats the stink bug egg host, “killing it in the process and then bursting out as an adult wasp,” Beers said.
T. japonicus has not eradicated the brown marmorated stink bug in Asia but appears to be one of the more effective parasitoids, Beers said.
“What we can hope for is that it will keep the ambient population of brown marmorated stink bug down so we won’t have the huge buildup like we’ve seen on the East Coast,” she said.
Kim Hoelmer, a USDA research entomologist studying T. japonicus in a quarantine lab in Delaware, said lab research will continue and scientists will monitor the wasp’s natural spread.
“We don’t want to introduce a non-native wasp that kills native stink bugs beneficial to our crops,” he said. “So far, however, the research looks promising that this tiny prizefighter favors the brown marmorated variety.”