Scientists wage war on pervasive stink bugs

It was an absolutely false claim, but totally believable.

Early this year, a few news organizations reported that the brown marmorated stink bug was at the top of an Agriculture Department most-unwanted list, the nation’s No. 1 invasive species of interest, the most wanted fugitive among bugs.

As it turned out, the Agriculture Deparment had no such list. An apologetic spokesman said he misunderstood a scientist in the department and passed faulty information to reporters. But that doesn’t mean the agency isn’t out to kill this crop-munching pest from Asia that recently expanded to 40 states since it was first spotted in Pennsylvania 15 years ago.

To the contrary, entomologists are zeroing in on stink bugs, unlocking the mysteries of their behaviors, DNA and even scent, and preparing for an all-out war.

True to their nature, stink bugs — heavily concentrated in Maryland and West Virginia, as well as Pennsylvania — aren’t expected to go down easily, certainly not this summer. “The expectation is high infestation this year,” said Ames Herbert, an extension entomologist at Virginia Tech.

How do researchers know? “What we can use as a rough guide is the size of the population from year to year that overwintered,” said Tracy Leskey, a research entomologist for the Agriculture Department. “In 2012, the population was 60 percent higher than 2011. If they survived the winter, we will have many bugs starting in 2013.”

Unlike previous years, when scientists and farmers “kind of got caught with our pants down,” said Robert Shenot — who watched stink bugs damage more than half of his apple crop at Shenot Farm Market, a few miles north of Pittsburgh, in 2010 and 2011 — they will face an array of new weapons developed especially for them.

Last year, USDA scientists and researchers pinpointed a pheromone that male brown marmorated stink bugs emit while feeding; it attracts other males, females and even babies called nymphs to the meal.

They re-created the scent in a laboratory, built a trap and tested it along tree lines, on the edge of farms and in the middle of crop fields. Sure enough, the bugs crept to it and were exterminated.

The triangle-shaped device is a temple of doom, luring the creatures into grooves leading to the synthetic smell that calls them to dinner. Instead of food there is a pest strip, and a pesticide vapor puts them to sleep for good, said Christopher Bergh, a professor of entomology at Virginia Tech.

The traps aren’t killing enough stink bugs to make a sizable dent in the population, Bergh said, but they do give researchers and farmers an indication of how many are lurking and whether they should initiate search-and-destroy missions.

Farmers have to resist “the first knee-jerk reaction . . . to get out there and spray them with chemicals,” Shenot said. “Certain chemicals they tend to take a bath in and laugh at you. They feed a quarter-inch below the surface of the fruit, and you can’t get an insecticide in there. You can spray the stink bug there on your crop, and if another set of stink bugs fly in, they’re not going to be affected at all.”

After observing closely for two years starting in 2011, entomologists developed an improved kill strategy for soybeans, Herbert said. They noticed that stink bugs chewed at “the edge of soybean fields but not deep into the field,” he said.

“We’ve been able to exploit that,” Herbert said. They monitored 25 fields as farmers treated the edge with insecticides. On average, they sprayed 30 percent of the acreage and got 100 percent control of the pest.

“If you spray the edge of the field and it works, they’re saving a lot of money and time,” Herbert said.

It is an epic tug of war with no certain outcome. The brown marmorated stink bug was first spotted in 1998 near Allentown, Pa., after some crept out of a cargo ship, and the population exploded 12 years later, taking a $37 million bite out of the Mid-Atlantic apple crop and a $15 million chunk of Pennsylvania’s peach crop.

By last year, they were either detected or established in 33 states and the District, and then in another seven states as of May. “It’s possible that this bug gets established in every state,” Herbert said. “I don’t see any reason why they wouldn’t.”

Worried scientists at the USDA research lab in Delaware, and others in Oregon and Florida, have been eyeing yet another weapon for years: an Asian parasite wasp about the size of a pinpoint that preys on stink bugs’ eggs.

The federal scientists have carefully tested and retested the creature, hesitating for fear that it might become invasive itself, competing with native wasps for food and territory.

As they waited last year, nature produced a breakthrough. Native wasps that had showed no interest in brown marmorated stink bugs started to develop a taste for their eggs, just as they preyed on the eggs of native stink bugs.

In addition, native birds started snatching and eating the Asian bugs, a breakthrough in the fight against a foreign pest with no natural predator.

“There’s more evidence now that natural enemies are starting to adapt to stink bugs,” Herbert said. “This is one of hundreds of invasive pests that have invaded the U.S. in the last 100 years, and most of them we’ve learned how to deal with them.”

Trouble is, Herbert said, you should never be overconfident with bugs. “Insects will make a liar out of you every time,” he said.

Darryl Fears has worked at The Washington Post for more than a decade, mostly as a reporter on the National staff. He currently covers the environment, focusing on the Chesapeake Bay and issues affecting wildlife.
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