Reprinted from Maine Public Broadcasting Network
Reported By: Tom Porter
State conservation officials are keeping a serious eye out this year for signs of an invasive beetle that destroys ash trees. The emerald ash borer has had a devastating impact on ash tree populations in the Midwest since it arrived from Asia nine years ago, and has now been seen in parts of the Northeast, including New York state and Quebec. It has not yet been spotted in Maine, but scientists say that doesn't mean it's not here. One method of detecting the beetle is to set up traps in the trees. These purple objects look like kites, and you may well have seen hanging from trees alongside the road. But there's also another method to help identify early signs of the dreaded beetle that involves the help of another insect.
On this playing field just yards from I-295 in Freeport, Forest Service entomologist Colleen Teerling holds between her fingers a small female wasp--one of the newest weapons in the fight against an invasive pest.
"Cerceris fumipennis," (left) as it's called, is harmless to humans--it doesn't sting. But if you're a beetle, watch out.
"You can see she's stressed out, she's trying to fight me, you can see the little yellow spots," she says. "It hunts native beetles that are related to emerald ash borer, so when emerald ash borer comes into an area it's really good at finding emerald ash borer."
We're standing in one of the baseball diamonds at the Middle School, a favored habitat of this much-treasured predator wasp. Teerling (below right) points to several little holes in the sandy ground, each the size of a pencil tip.
"We tend to find them on baseball diamonds, and often abandoned gravel pits," she says. "They like hard-packed sandy soil, they like it nice and open and sunny and not a lot of vegetation, and they need to be somewhere near trees, because trees are kind of their grocery store."
However, it's not as a predator that the Maine Forest Service is interested in using the cerceris wasp: Teerling says they would not consume sufficient numbers of the beetle to have an impact. She explains that the cerceris wasp is most useful as a bio-surveillance tool--nature's own early warning system.
She's here to train volunteers to monitor wasp colonies like this one and keep a particular eye on what they're eating. Using what looks like a butterfly net, volunteers are expected to snag a wasp as it returns to the nest with its prey. The prey is then sent off to a lab where scientists will determine whether the dead beetle is indeed the emerald ash borer--or EAB (below).
Teerling says one of the most important things for EAB management is early detection. "If we find an infestation early, we've got a lot more management options," she says. "If we find it late and it's spread hundreds of miles, there's very little we can do other than watch ash trees die."
"We want to make sure that we're sensitive to the way Maine communities will respond to this when it does become a problem, because we do expect that the insect will find its way here within the next few years," says Jan Santerre, the director of a new program overseen by the Forest Service to prepare Maine communities for the invasion of pests like the ash borer.
She's working on a pilot project in the nearby town of Brunswick, to identify cerceris colonies and monitor them for signs of the emerald ash borer. But why Brunswick?
"Brunswick, because they have an active street tree program, they have a municipal department that deals with trees, they have ash trees," Santerre says. "That was a big part of it."
Click here for more information on Maine's preemptive war against the emerald ash borer. If you'd like to be a volunteer, click here.