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Chambersburg Public Opinion: Stink Bugs Just Waiting For Warmer Weather


Now that you're over winter's last hurrah, it's time to think spring - and stink bugs.

Plenty of the pests crawled in for a long winter's nap, but scientists can only guess what that means for the 2013 growing season. A few early risers ventured out of the crevices on warm winter days, but many more are as snug as bugs in a rug.

They are waiting for 62 degrees, the critical temperature that activates them, and for the 14 hours of daylight that turns on female stink bugs. Scientists in recent months have researched the private lives of brown marmorated stink bugs, known as BMSB in pest management circles. And they are learning more.

"It almost seems that the important factor for the BMSB population is not what happened last year, but how good conditions will be in the spring of the current season," said Greg Krawczyk, Penn State Extension tree fruit entomologist. "We went into winter with relatively big populations, but based on experience from the previous three seasons, it really does not provide any indication of what will happen this coming season."

The recently invasive bug has the potential to suck the profits out of fruit and vegetable crops besides smell up sunny sides of living rooms.

In 2010 stink bugs did an estimated $37 million damage to apples in the mid-Atlantic states. Their population was huge at the end of 2010, but the next year their numbers were down. The bugs made a comeback in 2012.

Krawczyk blames the warm springs, not the number of bugs that huddle up in winter.

"Both 2010 and 2012 springs were warm and early, so probably whatever bugs survived the winter found perfect conditions to enjoy the season," he said.

Tracy Leskey, a U.S. Agriculture Department research entomologist, has said that BMSB populations at the end of 2012 were 60 percent larger than those a year earlier.

So there's a potential for hordes of stink bugs in 2013. The arsenal for defending crops and gardens has not changed much. Pesticide applications must be a direct hit.

"So a simple exclusion, such as nets, probably will provide a much better protection than any insecticide," Krawczyk said.

Spraying the edges of fields may not be the best solution for farmers, according to David Biddinger, Penn State Extension biocontrol specialist. Stink bugs fly 1.5 miles while bees fly just 100 yards from their hives.

"There's unintended consequences to this spraying," he said.

Pyrethroid pesticide also can act as a fertility drug, according to Biddinger. Exposed insects can lay more eggs and have more generations in a year. "At this moment neither dinotefuran nor bifenthrin are registered under EPA Section 18 emergency registration, but we are planning to request those registrations again," Krawczyk said. "Last year, the EPA did not let us use them until sometime mid-summer, so most likely we will again not know the status until the summer."

Bifenthrin is registered for homeowners' use, he said. Products with the active ingredient are available in garden shops of many stores. "When you spray the insecticide you will kill BMSB adults and nymphs, but the remaining dry residue is not active after a very short time, and will not control new BMSB adults arriving continuously from surrounding wild vegetation, such as ornamental trees," he said. Pesticides are not the long-term
solution, according to Biddinger.

Other potential controls of stink bugs are in the research stage. The bugs are attracted to some lights and some pheromones.

"We are getting there, it just takes time to find the best combination of various methods," Krawczyk said.v The combination of methods employed to control insects is known as integrated pest management. The BMSB set back by years integrated pest management in orchards.

Any biological component in IMP for the BMSB appears to be a long way off.

In the 15 years that the BMSB first appeared in Allentown it has spread from coast to coast. The Asian native thrived in an unfriendly environment full of potential predators and organisms that could have checked its survival.

"BMSB still managed to increase its numbers and become a pest," Krawczyk said. "This tells you by itself about the possible efficacy of our native beneficial organisms in reducing BMSB populations."

Spiders, mantids, lacewings and even birds may feed on BMSB adults, nymphs and eggs, but they switch on and off depending on what food is around, he said.

Biddinger is a little more optimistic.

"Natives get a taste for something exotic," he recently told Franklin County fruit growers. "They key on the smell of the stink bug. Over time they will adjust."

Both Biddinger and Krawczyk downplay expectations for a quick fix by importing an exotic wasp that goes after stink bug eggs. The Trissolcus wasp lays its eggs inside stink bug eggs and the wasp larvae feast.

The parasitic wasp needs U.S.D.A. approval, and some native stink bug species feed on insects that harm crops in the U.S.

"It will still be a long way before its impact on BMSB population will become visible," Krawczyk said. "We have to rear enough of them, learn how to release them and make sure they will survive after the release."

The wasp also presents something of a Catch-22 as a method of control.

"Growers will not be able to use them in their orchards or fields anyway, since their goal is not to have BMSB in their orchards or fields," Krawczyk said. "The wasp will not survive without food, and growers still have to control other 'normal' pests."

Will the non-native wasp survive in the wilds of North American?

Just one in seven introduced predators gets established, according to Biddinger.

And the invasives keep coming.

"Eleven new species are introduced in the U.S. each year without really trying," Biddinger said "I've
found three in Pennsylvania."

The latest, the Spotted Wing Drosophila has gone coast to coast in just three years, he said. With its switch-blade ovipositor, SWD "will go to town" on soft fruit such as blackberries and blueberries.
But the brown marmorated stink bug is unmatched for being unwelcome.

"The importance of BMSB did not change, the novelty did," Krawczyk said. "It's become just a good topic to keep complaining about."
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