Alarmed by new invader, Minn. ready to strike back at stink bug

Homely, smelly and destructive, the brown marmorated stink bug is the very definition of the unwelcome guest.

But now that the insect has gotten its creepy little toehold in the state, scientists are taking steps to head off one of the newest invasive species to hit Minnesota.

Since first being discovered in St. Paul in 2010, the bug — which emits a pungent smell often compared to dirty socks — has been spreading like wildfire across nine counties in the Twin Cities metro area and making inroads in Duluth and southeastern Minnesota as well.

The insect eats just about anything and is known to attack at least 300 different kinds of plants. It goes after garden vegetables and row crops, attacking the seeds of corn and soybeans.

Both Mark Abrahamson, an entomologist with the state Department of Agriculture, and Bob Koch, assistant professor and extension entomologist with the University of Minnesota, have made the case that the state must try to head off the stink bug invasion before they start to do serious damage to crops and the environment.

In 2010, the insects did catastrophic damage to crops in the mid-Atlantic states, where the species first burst on the scene after arriving from Asia in the late 1990s. Now found in 41 states, the insects have not reached that level of concern in Minnesota. At least not yet.

"We're fortunate that we have a little bit of lead time on this," Abrahamson said. "We've got a few years before this will be a substantial problem."

But the bugs are coming, based on how they have been spreading elsewhere. Experience suggests they will first become a nuisance home invader — even worse than Asian lady beetles or box elder bugs — and then move on to become a significant plant pest, threatening both agriculture and the environment.

That's why Abrahamson and Koch have joined the state and the university for a pre-emptive strike, asking the state for $266,000 for a three-year program targeting the bugs.

The Legislative-Citizen Commission on Minnesota Resources, which decides on how money from the lottery-generated Environment and Natural Resources Trust Fund is spent, backed the request last fall. The Legislature approved the expenditure.

The project has two parts, Abrahamson said. The state Agriculture Department will monitor the insect to get a better handle on where it has spread, and the university will try to identify a biological control for the bug.

Starting next month, the Agriculture Department will be looking for volunteers who will be trained and equipped to monitor the bugs, Abrahamson said. That will be done by trapping them, much like gypsy moths and other insects.

"On the East Coast, they got surprised when this first became a problem," Abrahamson said. "We're trying to avoid that. We want to make sure we know where it's going."

Many of those volunteer trappers likely will be farmers who stand to be most harmed by stink bugs.

The bugs seem to prefer living in trees and are especially drawn to apple orchards. That probably explains why they were found near La Crescent, the heart of Minnesota's apple-growing country.

"It cuts across all of our agricultural sectors, as far as being a serious pest," Abrahamson said.

While the bugs have been responsible for plenty of direct environmental damage, they also have forced farmers to use a lot more pesticide in response — in one study, a fourfold increase, he said.

A biological control would reduce that indirect harm to the environment.

The university, with help from the U.S. Forest Service, will work to identify other insects that could control the bug. A leading candidate, Abrahamson said, is a stingless wasp that acts as a parasite, injecting its eggs into those of the stink bug. When the wasps' larvae emerge, they consume the stink bugs' eggs.

There are several key questions the research needs to answer. They include figuring out if such a wasp could survive the Minnesota winter, and making sure that such a wasp doesn't pose harm to other species or the environment. That meticulous effort could take several years, Abrahamson said.

Jim Anderson • 651-925-5039 Twitter: @StribJAnderson