Wasp weapon to fight Oregon stink bug

Oregon pursues biocontrol of brown marmorated stink bug
By Oregon Department of Revenue

In some ways, it’s a race against time. It appears the potentially devastating brown marmorated stink bug is spreading in Oregon and populations of the insect pest are expected to jump over the next couple of years. Meanwhile, research is underway in Oregon and two other states centering on a tiny wasp, which happens to be a natural predator of the exotic stink bug, to see if it can be an effective biological control agent. In a best case scenario, the good bug will be able to go into battle about the same time the stink bug population takes off.

Oregon wants to avoid the extensive damage Pennsylvania and other states have 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. Pennsylvania has reported major losses the past couple of years for apples, peaches, grapes, tomatoes, and many other fruits and vegetables that also grow in Oregon. The list of crops and plants the stink bug won’t feed on is probably shorter than the list of crops and plants it likes. The bug even feeds on maple and cedar trees.

The brown marmorated stink bug was first discovered in 2004 as a home pest in Portland. Additional sightings initially took place in urban areas. But the past couple of years, the bug has been found in such agricultural production areas as the Willamette Valley and Hood River.

“On a pest risk scale of one to ten, I would say the brown marmorated stink bug is a 15,” says Helmuth Rogg, manager of the Oregon Department of Agriculture’s Insect Pest Prevention and Management Program. “We don’t want to make it sound too alarming, but we want people to be aware that there is great potential for this to be a very, very bad pest. Hopefully, time is on our side and we can avoid the big outbreak we’ve seen in eastern states. Biological control can help.”

ODA is the lead regional agency for conducting research involving Trissolcus halyomorphae, the imported wasp that acts as a parasite of the brown marmorated stink bug. ODA has received $116,147 from the US Department of Agriculture as part of a Farm Bill funding package addressing pest and disease management. Florida and Michigan are the other two states looking at the same good bug to treat the bad insect pest. The tiny wasps were collected from Asia– also home to the brown marmorated stink bug– and have been provided by USDA’s Agricultural Research Service (ARS). Oregon was a good candidate for the funds because it has the pest to begin with, ODA has the expertise in biological control, and Oregon State University has the quarantine facility needed to rear the insects and house the research.

“It’s a perfect choice for a classical biological control program,” says Rogg. “We have an exotic pest that comes into a new environment without its natural enemies where it can easily multiply. Parasitic wasps are found in its native Asia, brought to the US, and tested in the lab. Hopefully, biocontrol will be successful in controlling the brown marmorated stink bug because there aren’t really any other viable management options at the moment.”

A year ago, ODA received permission to import the tiny good bugs– classified as parasitoids from the original ARS rearing facility in Delaware. The research program set up shop at OSU where not only was a colony of parasitoids established over the winter, but a colony of brown marmorated stink bugs as well. Research confirmed that the adult female tiny wasp lays its eggs inside the brown marmorated stink bug eggs. As a result of the parasitization, the stink bug egg does not survive.

The big concern, and the reason it is way too early to consider the biocontrol agent a success, is whether or not the parasitoids will similarly impact native stink bug species. Not all stink bugs in Oregon are bad, and researchers want to make sure non-target species won’t be affected.
“We’ve made strong progress this past year in establishing the colonies,” says ODA entomologist Barry Bai, who is working with an OSU graduate student to conduct the research. “Our goal right now is to test native species to make sure the parasitoids won’t go after them. It’s a long process. We need to test several generations of parasitoids to make sure they don’t affect the good stink bugs and efficiently deal with the bad ones.”

While ODA and its cooperators test out the biocontrol agent on non-target species this summer, similar work is being done in Michigan and Florida with native stink bugs in their respective regions. All data will be shared and evaluated before any final decision is made to allow release of the tiny wasps. 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.

“Maybe by 2015, there will be some limited, restricted field releases by ARS,” says Rogg.

Other imported natural enemies of the brown marmorated stink bug are also under consideration. Everyone wants to see how promising the first biocontrol agent is before moving onto the next one. It could be that a combination of parasitoids will be necessary to control the bad stink bug.

ODA successfully conducted similar research on biocontrol agents for cereal leaf beetle before the good bugs were released in crop production areas. They are currently doing a good job controlling that pest.

“We’ve done this sort of thing before,” says Rogg. “If it all works out, there is hope down the road that these parasitoids will help keep brown marmorated stink bug under control. It’s really a difficult pest. There is no monitoring tool as traps don’t seem to work. There appears to be no other good control tool, including pesticides. So the big hope is for biological control.”

The first tool in the tool box may be the tiny wasp currently being tested in a quarantine facility in Corvallis. In a best case scenario, the parasitoid will take up permanent residency in Oregon to control the brown marmorated stink bug for years to come.

Video of parasitoid life cycle and impact on brown marmorated stink bug eggs

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

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