Many of Vermont’s best-loved trees face serious threats from invasive pests that have destroyed millions of trees in some states. One of the most troubling is the emerald ash borer, a deadly forest predator which has no known, effective treatment. The insect hasn’t yet reached Vermont, but the state is getting ready for it.
In the woods of Townshend State Park, forest protection specialist Jim Esden is girdling an ash tree. With its flow of nutrients interrupted, the tree will die within a year. But the sacrifice could help detect the presence of the tiny beetle that could kill many more ash trees: the emerald ash borer.
Esden says the insects also girdle the trees, by tunneling beneath the bark.
"The female will lay her eggs in the crevices of the bark," he explains. :The larva will emerge from the egg and eat through the bark and eat through the cambium and phloem layer. It only takes two to four years for an infested tree to die."
Esden makes a shallow cut with his bow saw around the tree’s circumference.
"And then about eight inches down we’ll do that again," he says. With a draw knife, he scrapes away the bark between the two saw lines. He says the dying tree will give off volatile oils that attract the iridescent green insect in its flying stage.
"And if there is emerald ash borer in the area, we hope that it will be attracted to this tree," Esden says. "They’ll lay their eggs and before the hatched out larva can mature and leave this tree, we’ll cut it down and peel the bark off to look for those larvae."
The emerald ash borer was first detected in this country in Detroit in 2002. Scientists think it came from Asia in packing materials.
So far early detection is the only realistic defense against the fast-moving pest, which is already killing trees on all sides of Vermont's borders. Esden says chemical treatments can sometimes help individual trees on lawns or in parks survive an infestation. But the treatments aren’t a practical solution in a state that has roughly 160 million ash trees.
Scientists are searching for a way to combat the infestations. But Esden says that’s going to take time.
"So our strategy in Vermont is not to eradicate, but simply slow down the spread of emerald ash borer," he says. "And that’s where citizen scientists are being so helpful."
Hundreds of volunteers have joined the effort to detect and contain the emerald ash borer and other pests that are threatening Vermont’s woods, including the hemlock woolly adelgid and the maple-loving Asian long-horned beetle.
On a recent Saturday a dozen volunteers were in Wilmington for the Forest Pest First Detector training. The program is by UVM Extension and several state and federal agencies. Volunteers learn how to recognize the pests in their adult and larval stages. They leave equipped with educational materials and handouts to alert their neighbors to the threat.
Betsy Whittaker attended the Wilmington training. Whittaker is a member of the Dummerston Conservation Commission, which had a small grant last year to map the town’s prominent ash trees.
"We presented our map to the select board and posted it in the town offices," Whittaker says. "We also talked with the town road crew and the tree warden. We wanted to alert people that the emerald ash borer is on its way -- if it's not already here -- so that we can make plans to contain it when it gets here."
One of the best containment strategies is to restrict the movement of wood. Forest pests often enter a region on firewood brought into campgrounds and vacation homes.
Whittaker has been visiting all the camping areas in her town. She’s aware of the dire predictions, that the ash tree will go the way of the chestnut and the elm. But she’s hopeful that won’t happen. And she says that when the ash borer is spotted in Vermont, it will be a volunteer who makes the discovery.