Tiny wasps could curb a massive stink bug invasion

USDA researchers in Delaware are working to find a safe way to dispatch the region's newest pest

  • Kathy Tatman is a biological technician at the USDA lab in Delaware. She takes a close look at a container of parasitic wasps that they are studying to help curb the stink bug problem.
Kathy Tatman is a biological technician at the USDA lab in Delaware.… (Lloyd Fox, Baltimore Sun )
February 28, 2011|By Mary Carole McCauley, The Baltimore Sun

Newark, Del. — — Maryland's newest terrorist life form — the brown marmorated stink bug — may eventually meet its archnemesis in the form of a tiny prizefighter of a wasp from Asia.

The parasitic wasps that are being raised in quarantine in a Delaware laboratory are not glamorous-looking bugs. They are black, stocky and about the size of the comma in this sentence.

But they are uncommonly efficient at hunting down and injecting their offspring into stink bug egg masses. In true horror-movie fashion, the larvae consume the stink bugs from the inside out. When the wasps grow into adults, they chew their way out, procreate — and go on the hunt for more stink bug eggs.

"Tests have shown that these wasps will destroy up to 80 percent of the stink bug population," says Kim Hoelmer, the U.S. Dept. of Agriculture scientist in charge of the project. "They're efficient egg-stinging machines. For something so tiny, it's absolutely amazing the behaviors that are hard-wired into their little brains."

Stink bugs aren't a threat to human health. And if they were merely odoriferous and annoying, chances are that the nation's top bug experts wouldn't be going to so much trouble to locate and develop an insect assassin.

But not only do stink bugs represent an unprecedented threat to U.S. vegetable farms and orchards, they have the potential to drive up food prices just when the nation is struggling to emerge from a recession. Bug experts say that the Asian wasp may be one of their best tools for keeping the stink bug population down to a manageable buzz.

"I've never seen such a serious pest enter the U.S. agricultural system," said Tracy Lesky, research entomologist with the West Virginia-based Appalachian Fruit Research Station, "if only because they attack so many crops."

Populations of stink bugs have been increasing steadily in Maryland for the past five years, and are poised to invade the state in record numbers during the coming growing season.

"I think we're going to have a bumper crop," says Michael Raupp, an entomologist at the University of Maryland. "If 1 in 10 people had stink bugs in 2010, 9 in 10 people will have them in 2011."

Hoelmer and his team have been importing and studying the parasites since 2005.

Because the wasps are not allowed inside the United States except for research purposes, technicians must don biohazard suits before going through a set of five pressurized locked doors inside the Louis A. Stearns Laboratory, where the wasps are housed.

Inside the quarantine rooms, research technician Kathy Tatman stuck a wad of cotton inside a piece of plastic tubing. She inserted the other end of the tube into a petri dish in which live wasps are kept, and inhaled through the cotton until several female bugs were pulled up into the tube. Tatman moved the tube into a second petri dish containing a fresh layer of pale green stink bug eggs, breathed out, and deposited the mama wasps on a nearby leaf.

Once the wasps find the egg mass, she said, they will almost certainly "sting" every one, eventually killing the embryonic stink bugs inside.

Preliminary indications are that wasps are effective, Hoelmer said, and, just as important, won't attack other, more beneficial bugs.

But establishing the necessary scientific proofs takes time. If all goes well, Hoelmer hopes to have authorization to release the Asian wasps into the environment some time in 2013.

For desperate farmers, two years might not be soon enough. So last month, Maryland joined nine other states and submitted a grant proposal for $22 million to the National Institute of Food and Agriculture to explore both long and short-term solutions to the stink bug problem.

Hoelmer's wasps are part of that proposal. So are a group of scientists in Beltsville who think they have identified the stink bug pheromone, or chemical signal, that causes a large amount of the insects to congregate. If researchers can replicate the pheromone, they could potentially trap and kill the bugs before they damage the fruit.

Researchers also are trying to come up with pesticides that will poison stink bugs, repellants that will deter them, fungi that will attack them, and a various other methods.

"We're taking a cafeteria of different approaches," Lesky said.

"We still don't have any proven tools, but we're way ahead of where we were at this time last year. We have all the pieces in place, and we're working to find solutions as quickly as we can."

Right now, stink bugs are causing the most damage to the mid-Atlantic region. But it's only a matter of time before the epidemic reaches the rest of the nation.

Stink bugs are portable, voracious and formidably adaptable, and populations of the insect have been verified in 33 states.

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