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Forest Invaders

By Shelly Stiles
Sometimes it feels like we’re at sea on the waves of history, unable to steer except clumsily through the flotsam in the water with us.  I felt that way recently at a workshop on invasive forest insects, presented by Forests, Parks and Recreation forester Jim Esden and sponsored by the Bennington County Sustainable Forest Consortium. On the screen before us was a map of the spread of the emerald ash borer (or EAB) since its discovery in Detroit in 2002. The mitten that is Michigan was deeply red (infested) on the palm and the thumb, and pocked with red elsewhere – as were northern Illinois, Indiana, and Ohio; eastern Pennsylvania; Maryland; various Lake Ontario locations; and a community south of Montreal, about thirty miles from the Vermont border.

Then Jim spoke of, not a life raft, but a lawn chair. A lawn chair, a cooler of cold drinks, sunscreen and sunglasses, and a butterfly net, he said, are some of the tools of the trade when it comes to emerald ash borer in Vermont. They are used to monitor the comings and goings of a native wasp known as Cerceris fumipennis (it has no common name) which preys on metallic-looking, wood-boring beetles, among them the EAB, bringing them home to their nests to feed to their developing young. An examination of the adult wasp’s baggage (the wasps don’t sting) can provide information on local beetle populations. Elsewhere in the country, this “biosurveillance” has been found ten times as effective as traps, tree examinations, and other methods in discovering the presence of emerald ash borer. And no Dramamine is needed.

The wasps prefer well-drained unvegetated locations in full sun. Ball diamonds, campsites, and unpaved parking lots are good candidates for Cerceris sleuthing. The ground around the nests isoften littered with eye-catching beetle corpses. In Vermont, so far, none of the corpses have been those of emerald ash borer. (If your ball team would like to adopt a diamond for Cerceris monitoring, we’ll arrange for training. Contact us at 802 442-2275 or

That tide is likely to change, however. The insect isn’t a strong flyer, but its human accomplices get around very well. The beetle seems to be hopscotching across the middle and eastern part of the continent on firewood purchased for the home or the campsite. The threat of emerald ash borer is one of the reasons Vermont State Parks prohibit firewood originating from an area more than fifty miles away. In the Green Mountain National Forest, only kiln-dried firewood with its original packaging and label is permitted.

EAB isn’t the only non-native insect of concern. Others include a European wood wasp, a destructive pest of pines and other softwoods (one specimen was found in Lamoille County in 2007); the Asian longhorned beetle, which preys on maples and other common northern forest species (and which is present as near by as Worcester, MA, about forty-five miles from the Vermont border); and hemlock wooly adelgid, a pest of hemlock only, which has been found in the Connecticut River watershed in Vermont. In fact, I received a call two days after Jim’s workshop from a second home owner in East Jamaica. He thinks the adelgid is present on mature hemlocks in his yard.

Citizen monitoring by landowners and volunteers will be critical in slowing the spread of these pests into and around our state. Good housekeeping will also be important. If you buy firewood, confirm that your supplier has harvested it from safe locations. (Many loggers have attended workshops on preventing the spread of these pests, and are proud to “walk the talk.”) Don’t move firewood irresponsibly. When purchasing nursery stock, make sure that the stock has been inspected.

Why? Because, as the conservationist Aldo Leopold said, “That the situation is hopeless should not prevent us from doing our best.”

Shelly Stiles is the district manager of the Bennington County Conservation District, whose mission is promoting rural livelihoods and protecting natural resources in southwestern Vermont.

This column appeared in the Bennington Banner in April 2010, as one of the BCCD’s Conservation Currents pieces, a bi-weekly feature written by BCCD board and staff members since August 2006.