Right on time for spring, the malodorous stink bug arises once again

     Stink bug (AP Photo/Matt Rourke)

    Stink bug (AP Photo/Matt Rourke)

    The stink bug is emerging from its winter refuge to mate. Following this renewal, it will go on to ruin crops and drive homeowners to distraction. We are in the springtime of an infestation.

    The robins, the daffodils, the Phillies — how we love this long-awaited spring.

    Yet with the season we also confront a nuisance and downright marauder that seeks to propagate by untold millions. That would be the brown marmorated stink bug, so named because it emits an “eau de …” — well, the best description I’ve heard is “smelly socks, burnt rubber and cilantro.”

    The stink bug is emerging from its winter refuge. Sensing the light of longer days, it is exiting houses in the Philadelphia area, across Pennsylvania, and throughout the Mid-Atlantic states. It goes forth into nature to mate. Following this renewal, it will go on to ruin crops and drive homeowners to distraction.

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    We are in the springtime of an infestation.

    It is also the time when entomologists look for signs that the stink-bug population might be falling. They bait traps with ultraviolet light. Or they employ a come-hither chemical — an “aggregation pheromone” — that the male stink bug emits to attract his kind, male and female alike and the nymphs they produce. You don’t want this stuff in your bathroom. Placed near favorite haunts of stink bugs, orchards being an outstanding example, the traps capture early out-of-doors migrators. Hence an indication of the size of the population that survived the winter.

    It stands to reason that our recent brutal winter would have taken its toll, if not on stink bugs that nestled in attics, then on those that sheltered in the hollows of dead trees. Since a typical winter in the Mid-Atlantic kills about half of the stink-bug population, the recent cull must have been … 90 percent?

    But no. From a sentinel with a comprehensive view, the U.S. Department of Agriculture, we have this report: “The stink bugs seemed to have survived just fine.” So says Tracy Leskey, a USDA entomologist who heads a national effort to combat the pests.

    And locally? “We definitely have been getting calls. We get calls in the spring every day.” That’s from Hope Bowman, an entomologist at Western Pest Services who works in southeastern Pennsylvania, South Jersey, and Delaware.

    So stink bugs are outdoors and in copula. The females will each lay approximately 300 fertilized eggs through the summer. They may still be depositing egg masses even as their daughters start to lay eggs. A plague revives its momentum.

    The menace spreads

    It apparently started in Pennsylvania. The first reports of the brown marmorated stink bug, a native of Asia, came from Allentown during the 1990s. The officially confirmed sighting dates from 2001. Perhaps the visitor had caught a ride on a cargo ship, but whatever the transport, it alighted on a broad continent where it had no natural predators, no reason to spray the defensive, foul-smelling whiffs that issue from its thorax.

    In 2003, Leskey noticed an insect at a service station where she stopped while driving in Maryland. The bug had come to rest on a gas pump. It was about an inch long, its body shaped like a shield and marbled in shades of coppery brown — a pattern that she, as an entomologist, would know to call “marmorated.” Leskey alertly took the bug captive in a Q-tip holder, photographed it upon return to her lab, and sent the photos to a taxonomy group at the Smithsonian Institution. She got the confirmation: Halyomorpha halys, the brown marmorated stink bug.

    So the stink bug had found its way into three states, at least. There had been a sighting in New Jersey the year before. Even so, Leskey says, “We had no idea at the time what was ahead of us.” The count today is 41 states, plus Canada.

    Pennsylvania and other Mid-Atlantic states remain the hardest hit, and the biggest hurt is on the farm. The stink bug is a voracious eater. Using its tubular mouthpart as food-lance and straw, it assaults grapes and apricots, peppers and pears. It devours corn and pockmarks tomatoes. It feasts on soybeans. It leaves trees and shrubs with weeping wounds.

    In 2010, a breakout year for the stink-bug population, peach growers in Pennsylvania lost roughly a third of their crops. Apple growers across the Mid-Atlantic valued their loss at $37 million. So bad were the showers of stink bugs that one farmer drove his harvester under blue skies with the windshield wipers turned on. Farmers and entomologists conferred. What had been a scientific working group became the federal project now led by Leskey from a research station in Kearneysville, West Virginia, and comprising some 50 scientists at 10 universities.

    Today, hardly anything about the stink bug goes unstudied. Its range of depredation is mapped, its power of flight recorded. As a hitchhiker in car trunks, packing crates, and anything else that moves, it hardly needs to be a marathon flier. Yet a stink bug fastened to a laboratory contraption something like a carousel will go round in a dizzying number of revolutions. A typical performance is a mile or two in a day. The best of breed can do 20 miles and up.

    Allentown to Philly? A mere weekend excursion.

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    Brown marmorated stink bug map (PDF)

    Brown marmorated stink bug map (Text)


    An attempt to cull their numbers

    As a stop-gap, researchers have determined the most effective pesticides among a class called pyrethroids. It may be enough to apply pesticides to only the edges of crop fields, because it has been discovered that stink bugs attack from the periphery. The longer-term objective is to identify potential predators in North America — wasps, spiders, beetles — and coax them toward a taste for stink-bug eggs.

    “It’s a little like eating chicken all your life and then being presented with steaks,” says Anne Nielsen, an entomologist at Rutgers University. A wasp has been brought in from Asia, too, though it remains under quarantine pending studies of what unforeseen destruction it might cause even as it goes about controlling the stink-bug population.

    If the wide-ranging appetite of the brown marmorated stink bug sets it apart from stink-bug species native to North America (some 250 of them), so does another trait: a cold-weather affinity for the built environment, that is, your house and mine. There is little solace in being told the intruder is harmless.

    It sneaks up on you. You think you’re alone, comfortably settled into your easy chair. Then sounds the annunciatory buzz. You look up from your book to see a speck in manic flight. Wild dives. Frenzied ascents. Drawn to light, the stink bug crashes onto the lampshade by which you’re reading. You reflect on the evolutionary chasm between yourself and this ancient arthropod, between your awareness and what must be, eerily, its own. It twitches a segmented leg, flies off, returns. A second of the species makes a collision landing on the shade, then a third. They congregate. Eyes like pustules bulge from opposite sides of the tiny, repugnant heads.

    You decide cohabitation is no longer an option. Nor, perhaps, is catch-and-release, unless you have found your true and gentle Buddha nature. Among means of disposal, there is only one to be shunned: Squish a stink bug, and it will have its revenge in a final malodorous puff.

    How to trap stink bugs

    I know all this from only a few encounters in suburban Philadelphia. Compared to the experience of others, mine is slight indeed. One scientist has published the study he did while vacuuming stink bugs out of his home in Maryland. He actually counted them: 29,205 over six months. You wonder how many miles of caulk have been used across the country to seal windows, doors, siding, pipes, and chimney flashing, all in an effort to bar entry to the stinkbug on those cool autumn days when it seeks a place to settle down for the winter.

    Yet stealthy as stink bugs seem on entry to a house, they can be clueless in departure. They could fail to find the front door even if you held it open and said your goodbyes. So here’s some news you can use if your unwanted guests are still bumbling toward the light of spring. Thomas Kuhar, an entomologist at Virginia Polytechnic Institute and State University, and John Aigner, a grad student, have reviewed several stink-bug traps. The best was simple and cheap: an aluminum-foil roasting pan, filled with a drowning bath of soapy water, and set under the glow of a desk lamp. Some households testing this trap reported that it caught up to 144 stinkbugs a week.

    There are more to be caught.

    “If any insect was going to survive that cold spell,” Kuhar says, “it was the brown marmorated stink bug.”

    Richard Koenig is a NewsWorks contributor. Formerly he was a reporter for The Wall Street Journal. He lives in Newtown Square, Pa.

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