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The 007 Wasp:

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Tuesday, 16 August 2011

The 007 Wasp: Vermont's Cerceris wasp is on the front lines against the emerald ash borer Aug. 13, 2011 Written by Joel Banner Baird BRANDON — Entomologist Trish Hansen is playing shortstop these days, fielding wasps instead of flies. From a distance, her actions resemble those of martial artist. On a scorching hot day earlier this summer at the Estabrook ball field in Brandon, she scanned the middle distance, almost motionless — then twirled and slashed the air with a long butterfly net. As often as not, she returned to her ready-pose, squinting beneath her big floppy straw hat. Hansen, a specialist at the Vermont Department of Forests, Parks and Recreation's Forest Biology Lab, bears no ill-will against her quarry. To the contrary: She's hoping to enlist the tiny, ground-nesting Cerceris wasp in a battle against a non-native beetle that threatens one of North America's most productive hardwoods: the ash. Cerceris fumipennis is sold on the idea. During its two-month airborne life, the female hunts down beetles belonging to the Buprestid family, a crew also collectively known as jewel-beetles or metallic, wood-boring beetles. As luck would have it, the emerald ash borer is fair game. The wasp's healthy appetite, coupled with its habit of dropping prey when disturbed near its next, makes it an excellent scout. When Hansen nets or spooks a Cerceris, she stands to learn more about what sorts of Buprestids inhabit the nearby woods. Emerald ash borers already have killed tens of millions of ash trees in Canada and the U.S.; nobody is counting on a thinly settled and short-lived wasp to eradicate the invader. But early detection provides foresters the only real chance of isolating and destroying the beetle, Hansen said. It's the same reasoning that has prompted the installation of so many purple traps in New England forests. "Biosurveillance" with Cerceris is similarly labor-intensive, but it pays higher dividends. Scientists working in Connecticut for the U.S. Forest Service determined in 2008 that a colony of wasps fetched as many emerald ash borers in one day as a purple trap did for an entire summer. Strange people Hansen has led the state's Cerceris WaspWatch program since 2009, when emerald ash borer populations were found within easy striking range of Vermont's forests — a mere 50 miles via New York or Quebec. As entomologists like to point out, the beetle easily can reach speeds of up to 65 mph — through the thoughtless transportation of infested firewood. Stricken trees can be slow to exhibit symptoms. Adults merely nibble ash leaves. Their larval offspring, however, tunnel hungrily through the trees' soft, sub-bark phloem layer in "a slow strangulation," Hansen said. In some circles, the beetles' march through North America is thought to be inevitable, unstoppable. Brandon resident Mary Lou Webster her husband, Bruce Jenson, take the contrary view. They have an untouched ash tree in their front yard, right across from the ball field where, earlier this summer, they spied Hansen and her husband, Luke Curtis, whirling butterfly nets — in the absence of any discernable butterflies. "We thought these were some strange people," Jenson said. Disney's bad dream Curiosity prompted the Brandon couple to cross the road. They volunteered shortly thereafter. Their task in July and August: Coax the nest-bound Cerceris to surrender its beetles for inspection. "This is biology at its finest," Webster declared. Hansen logged steal after steal in her notebook. Though all were shiny; none of the inert Buprestids matched the wanted poster. After documenting and collecting several more beetles, the humans moved on. "We don't want to leave the wasps destitute," Hansen said. As you might expect, Cerceris, packs a venomous sting. But its firing mechanism for some reason isn't suited to human targets, she said. And, she added, the wasp's distinct coloring on its head seemed to communicate affability. "It's the cutest thing. They look like they're smiling at you," she said. Webster demonstrated: She gently pulled a Cerceris from her net and passed it to a visitor, where it buzzed loudly and then vibrated itself free, in search of another Buprestid. The adult wasp doesn't eat all those beetles, Webster explained: It injects its prey with a paralytic venom, a designer drug that puts the beetle into a well preserved suspended animation that lasts for months in the wasp's underground brood chamber. The Buprestid's bliss-of-not-knowing ends when a wasp egg, laid in a chink in the beetle's armor, hatches into a larva and begins to feed. "It's not Disneyland out here," Webster said. Like fishing Last year, Hansen identified 38 active Cerceris sites in Vermont — six of them with more than 50 nests. After leaving Brandon, she and Curtis drove to Dewey Field in Rutland Town. "What a screaming place for wasp activity!" she wrote later in an email. "One actually hit me in the hat and dropped a nice coppery Buprestid at my feet." Along with other entomologists in New England, she's mapping Cerceris's front lines against the emerald ash borer. She admits to seeing spots before her eyes after a particularly busy day of biosurveillance. The stakes are high enough to keep her and her volunteers on the job. "It's a little like fishing," Hansen said. "You don't know what you'll get — and you don't want to leave: 'Just one more!'" http://www.burlingtonfreepress.com/article/20110814/GREEN01/108140304/The-007-Wasp-Vermont-s-Cerceris-wasp-front-lines-against-emerald-ash-borer?odyssey=mod|newswell|text|FRONTPAGE|p

 

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