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Asian stink bugs are here

Some creepy-crawly bugs, such as ants, flies and spiders, may be unwelcome in our homes. But at least they're familiar. We can deal with them.

For plenty of Marylanders, though, a new species of household pest is just insufferable.

"These are just so ugly, they're horrible," said Adele Hammerman, whose condominium in Baltimore's Deer Ridge community has become a hangout for the critters.

"I was in bed one night and there was one crawling on my finger, and another in my hair," she said. "Their legs look like spidery kind of legs, and they just creep along silently. You don't notice them 'til they're right on you. They're awful."

The brown marmorated stink bug, an invasive insect species from Asia, is turning up in homes across the Baltimore region. Residents have reported sightings in Westminster, Owings Mills and in Towson, where Virginia Callegary, 29, has been ushering them out of her home for weeks.

"I try to take them outside instead of killing them because they stink," she said. "But they just keep appearing. I don't know how they're getting in."

Mike Raupp thinks he knows.

"This is one of these bugs that comes in the autumn, along with the ladybirds," said the University of Maryland entomologist, author of the Bug of the Week website. "They're just trying to find shelter."

They'll slip under siding or shutters, and enter houses through vents and gaps in windows, and soffits, or in older stone foundations.

After hiding out inside our houses for the winter, Raupp said, they get active again as the weather warms up and begin looking for a way to get outside to feed and mate. Each female will lay enough eggs to make another 400 stink bugs.

But instead of exiting the premises the way they came in, some of the bugs wind up in our living spaces.

They can appear by the hundreds. "I got a call from a guy in Baltimore County who was vacuuming the things from the windowsills and baseboards," Raupp said.

"They seem to come out of the air, somewhere," Hammerman said. "I would be sitting by my computer and one would just come out of the air and drop right in front of me. At times I see them crawling around on the molding. I've seen them on the walls. I've found some dead ones."

The stink bugs first turned up in Allentown, Pa., in 1998. "And ever since they have been spreading out in all directions," Raupp said. "They began to hit Maryland five or six years ago … and now we're getting reports from all over the state. They're becoming more abundant throughout the region."

Stink bugs have become a serious pest in fruit-growing regions of New Jersey and Pennsylvania, damaging cherries, peaches and plums by inserting their sucking mouth parts into tender fruit, causing ugly scarring called "cat facing."

"I guess somebody must have thought it looked like a cat face. It never looked like a cat face to me," Raupp said.

The bugs could become a problem for Maryland farmers, too, he said. "They have the potential to be serious pests in soybeans."

Known to science as Halyomorpha Halys, the brown marmorated stink bug looks like a small brown shield with legs and antennae. Raupp thinks the term "marmorated" comes from a Latin word meaning "marbled," a reference to the coloring on their abdomens.

"Everyone's talking about them, and no one knows how to get rid of them," Hammerman said.

Scooping or vacuuming them up, and disposing of bugs and bags in the garbage is advised, Raupp said. Letting the bags sit in the sun a while to kill the bugs is even better. As non-native invaders, and agricultural pests, just setting them free outdoors is not the best plan.

"These are one of the guys on our dispatch list," Raupp said. "They don't seem to serve any useful purpose in this environment."

But making stink bugs angry in the process is a mistake.

"They've got scent glands that are used as a defense against predators, or misbehaving bug geeks," Raupp said. "Frankly, they stink."

Callegary found that out the hard way. "I killed one before I knew it was a stink bug," she said. "That was not fun. It stank. I can't really identify the smell. It smells like something you shouldn't be smelling."

Their stink is produced by scent glands that go into action when the bug is squashed or merely annoyed. It has been described as "unpleasant, foul, vile, noxious, powerful" and, worst of all, long-lasting.

Raupp said the best offense is a good defense. Homeowners need to close up those gaps in their homes that allowed the stink bugs inside last autumn in the first place.

"Sealing, caulking, weather-stripping, screening … anything that you can do that is good for energy efficiency will help keep these invasives out," he said. "We don't want people spraying inside their homes for these things."

Spraying pesticides around the outside doesn't make sense, either, Raupp argues. "They're ubiquitous outdoors, and they can travel long distances," up to a quarter-mile.

One novel scheme for killing them individually is to turn a can of compressed air upside-down and release its chemical propellant. It freezes the stinkers before they can trigger their scent glands.

Another is a 50/50 solution of Dawn or Ivory dish detergent and water in a spray bottle. A few squirts will kill the bugs or allow you to catch and dispose of them.

In the long run, the best remedy for the stink bugs might be natural predators, Raupp said. The problem is, they left most of theirs behind in Asia.

"I think there are some," he said. "Birds and toads may give it a try. We have native stink bugs, and they're preyed upon by many different kinds of birds and small mammals."

But the invaders "seem to lack an important enemy in this country," he said.

So, entomologists have begun to study some Asian parasitic wasps that might make good candidates for biological controls for the stink bugs here.

"It's our best option," he said. And it will attract plenty of research dollars. "Anything that pushes this out of the nuisance camp into the agronomic pest camp is going to accelerate the search for biological control agents."

That would be fine with Callegary.

"I do not enjoy bugs," she said — although her cats seemed to. "They like to play with them if they can get them, which they usually can't."

But even that feline amusement appears to be becoming a bore, she said. "Recently, they're not so interested. They're getting used to the bugs being there."

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