Using wasps to fight stink bugs in Oregon

Tiny wasps offer hope in battle vs. exotic stink bug
Imported natural enemies are being researched in Oregon
By Oregon Department of Agriculture,

Oregon’s ability to control an exotic stink bug that threatens agriculture may rest on a tiny insect that just happens to be a natural predator of the unwanted pest. It’s a classic case of biological control with good bugs being used to fight bad bugs. Among the interested parties is the Oregon Department of Agriculture, which hopes to find an effective way to battle Halyomorpha halys, better known as the brown marmorated stink bug.

“We first found brown marmorated stink bug in Oregon in 2004,” says Helmuth Rogg, manager of ODA’s Insect Pest Prevention and Management Program. “That first introduction was in Portland and most of the subsequent sightings were in urban areas. But in 2010, we started looking outside urban areas to see if the bug was on the move. We are now seeing it in areas close to agricultural production. That’s the scary part since the pest has a long list of crops it will attack.”

Oregon wants to avoid the extensive damage Pennsylvania has suffered because of the brown marmorated stink bug. What started out as a nuisance pest a decade ago in the Mid-Atlantic states has now exploded. Last year, major losses in Pennsylvania were reported for apples, peaches, grapes, tomatoes, and many other fruits and vegetables grown in the area. Some growers lost half of their crop. The stink bug even feeds on maple trees, which comes as a surprise to Rogg.

“This could turn out to be the bug from hell for us,” says Rogg. “Ornamental trees, hazelnuts, fruits, vegetables- you name it, the bug attacks it. Actually, it might be easier to list the plant hosts it won’t attack.”

ODA has started a more aggressive survey program this summer and will test various traps for the brown marmorated stink bug. Working closely with Oregon State University, ODA is specifically looking at major fruit production areas, including Medford, Hood River, and Milton-Freewater. The pest has already been located in various areas of the agriculturally-rich Willamette Valley.

The brown marmorated stink bug is common to Japan, China, Taiwan, and Korea. Like several other insects in Oregon- including box elder bugs and Asian multicolored lady beetles- the exotic stink bug seeks shelter in homes during the fall and winter months. Where the bug has become established, it can enter homes by the thousands, which can be stressful and disturbing to residents. As creepy and crawly as the stink bugs may be to homeowners, they won’t cause harm to humans. But they do represent a major problem for agriculture.

While similar in looks to Oregon’s native stink bugs, this one could be especially troubling in areas where it has no natural predators, parasites, or diseases to help control its population.

The US Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) is looking to find those natural predators overseas and bring them back to the states as biological control agents that have just one job- destroy the eggs of the brown marmorated stink bug. APHIS is working with USDA’s Agricultural Research Service and the Center for Plant Health Science and Technology to recruit the right bug. At the moment, the best bet is an egg parasitoid.

“These are tiny parasitic wasps that lay their eggs inside the eggs of the stink bug- effectively consuming or sterilizing the stink bug eggs,” says Rogg. “Eradication of the brown marmorated stink bug is not possible anymore. Biological control is our best choice for controlling the insect pest.”

The State of Oregon received a $100,000 grant from USDA to supplement the effort to find effective egg parasitoids for use against the brown marmorated stink bug. Currently, there are four promising species. Facilities at OSU in Corvallis, Michigan State University, and the Florida Department of Agriculture are rearing the bad bugs in order to provide hosts for the imported egg parasitoids. The next step in the research is finding out if the imported good bugs harm Oregon’s native stink bugs, some of which are beneficial to the environment in their own way. Assuming the imported parasitoids impact only the brown marmorated stink bug eggs, they would be reared in insectaries to attain sufficient numbers and possibly be released into the natural environment within the next couple of years.

Controlling bad stink bugs with synthetic sprays has not worked well in Pennsylvania. The species tends to be tolerant of many pesticides.

“We would prefer to use biological control because it is safe for the environment and safe for other beneficial insects in the field,” says ODA entomologist Barry Bai, who has worked on a similar project to control cereal leaf beetle in Oregon.

In terms of harboring brown marmorated stink bug populations, Oregon is about where Pennsylvania was three or four years ago. That doesn’t necessarily mean Oregon will suffer the same crop damage reported back east last year. But officials don’t want to roll the dice.

“It’s difficult to say what the brown marmorated stink bug will end up doing in Oregon,” says Rogg. “But with the experience of the Mid-Atlantic states, I don’t think we can afford to take any chances. It would be a big risk to do nothing.”

Detection surveys for the exotic insect pest are underway. As more is learned about the spread of brown marmorated stink bug, officials will have a better idea of how to use biological control efficiently and effectively. All this assumes that the imported tiny wasps only have an appetite for the exotic stink bug.

“We should know a lot more in about a year,” says Rogg.

Everyone is hoping that the egg parasitoids- the good bugs imported to battle their natural enemy, the brown marmorated stink bug- will take up permanent residency in Oregon for years to come.

For more information, contact Helmuth Rogg at (503) 986-4662.

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