Maryland Scientists Battling America’s Top Invasive Insect: Stinkbugs

Scientist in Beltsville are working to fight the obnoxious pest that invades homes and eats crops.

There are pests lurking in the woods nearby, hiding out in dead trees, waiting for the end of winter. Occasionally, you find them on your lamps, your windowsills, or in your storage space. Farmers find them on their peaches, sweet corn and soybeans. They move slow, smell bad.

They are the Department of Agriculture’s top invasive insect of interest and possibly Maryland’s most annoying bug: the Brown Marmorated Stinkbug (BMSB).

Not far from Howard County,  scientists at the Agricultural Research Service in Beltsville are attempting to locate weaknesses, habits or predators that will control their rampant population growth in North America.

Currently, there are no effective pesticides or biological control methods being used in North America to control large BMSB populations, according to stopbmsb.org, a website set up by the BMSB working group, a group of scientists studying the insect.

Last year, stinkbug populations were down compared to 2011, but scientists monitoring the bugs say hibernating populations that are in overwinter could bring a strong return of the bugs in 2013, according to NPR.

Most scientists point to the late 1990s as the time when BMSBs were introduced in North America, likely from China, according to stopbmsb.org. After introduction, it wasn’t until 2010 that the bugs became a significant problem, causing catastrophic damage to crops in Mid-Atlantic states, according to the website.

Don Weber, an ARS scientist in Beltsville, said the onslaught of stinkbugs in recent years is still a relatively new phenomenon.

“They became too widespread to eradicate before [scientists] realized the nature of the problem,” said Weber, who is currently researching the effectiveness of different lures to attract the bugs, which could eventually lead to commercial or residential traps.

“There are hundreds of millions out there,” said Weber.

He said the bugs eat a wide variety of foods, preferring plants with starchy, sugary tissue such as peaches, apples, tomatoes, green peppers and sweet corn. From spring to fall the BMSB move from plant to plant piercing food with its sharp beak to inject saliva, which dissolves the plant material so the bugs can eat it, according to Weber.

“There’s an obvious pattern of attack [in fields],” said Weber. “They move in from the woods and feed on the edges.”

“The worst kind of horror stories people have is when they’re surrounded by an orchard or soybean field and live in a single house in an open field,” said Weber.

Weber and the team at ARS are looking at a specific pheromone of the BMSB to see if this will help them control populations.

The pheromone is not the cilantro-y smell that gives the stinkbug its name, says Weber -- that’s a defense mechanism used to repel predators. Rather, the pheromone is used to attract other stinkbugs, as well as nymphs (young stinkbugs) to a feeding location. 

“The thought is that it’s an all-purpose pheromone,” said Weber. “It’s used to attract females. More males come because there are females coming in and nymphs probably come for the source of food.”

Ashot Khrimian, an ARS chemist, has been able to reproduce the pheromone and Weber is currently testing it in a number of traps.

Weber said in field tests he has conducted, the pheromone worked, attracting and capturing bugs in a pyramid trap. The problem though, says Weber, is the chemistry is difficult to replicate and it doesn’t seem to work when the bugs are looking for somewhere to hibernate. 

“What galls homeowners is when they get inside,” said Weber. “They’re looking for a place to overwinter. At that point they’ve finished feeding and are looking for a sheltered area where they are protected from the extremes of weather.”

As of right now, Weber isn’t sure how the pheromone would be deployed.

“You could attract more than you want,” said Weber. “We want to attract the bugs away from where people don’t want them. These are things we’ll start addressing this season [in 2013].”

While work continues on that, Weber said other scientists are studying natural predators for the bug. This includes parasitoid wasps. A lab in Delaware is testing six to eight strains of wasps to determine which one is the most effective at killing BMSBs, but it’s a delicate process, according to Weber.

“If you [introduce the wasps] without sufficient environmental checking, you could disrupt the balance of things,” said Weber.

When the BMSB working group met last year in June in Westminster, scientists ranked studying the basic behavior of the bug as the most important priority, with identifying a true pheromone as the second most and biocontrol agents as the third.

This summer, Weber said he’ll be working with his traps and lures based on the aggregation pheromone to determine their effectiveness.

“All summer, twice a week, we’ll be doing replicated treatments,” said Weber. 

As for homeowners preparing to fight the bugs this spring as they come out of hibernation is to be prepared, check out Patch's article on 10 ways to fend them off.

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