Dave Estey turns over a branch of evergreen needles while walking on the snowmobile trail behind the Wilton Reservoir. Underneath, so small they are only apparent upon a close look, are small, white dots.
“There it is,” Estey said.
The “it” is hemlock woolly adelgid, an east Asian insect that’s become a troublesome invasive species in the United States. It only impacts hemlock trees, but once it has taken hold on a specimen, it can completely kill the tree.
The aphid-like insect covers itself in a white, waxy substance that gives it its name, and will spend almost all its lifecycle in one place, only moving right after hatching to find a suitable feeding spot, and then attaching to the hemlock tree feeding on the sap at the base of the needles. This eventually kills the needles, and without the needles, the tree itself starves to death.
Estey, who only lives a short distance from the reservoir, said he first noticed a few trees with the infestation while walking his dog in the area.
“I’m always looking at the trees and keeping an eye out for things I know are a problem,” he said. “Finding it that close means I’m going to have it [near my home] soon.”
The woolly adelgid looks like tiny cotton puffs, no larger than one-sixteenth of an inch, clustered along the bottom of hemlock branches.
Hunter said he hasn’t seen the trees around the reservoir that have been impacted, but he’s aware the woolly adelgid is in Wilton, having found it on trees in the town’s conserved Heald Tract.
“They’re very significant, because they kill the trees they infest,” Wilton Conservation Commission Chair Bart Hunter. “There are very few treatments for it, and what treatments there are wouldn’t work well on acres and acres of hemlock.”
While there are spray treatments to deal with the pest, Hunter said, treating large amounts of trees is expensive, and usually the solution becomes to cut down the infested tree.
The pest is not a new phenomenon in New England. The woolly adelgid was first found in the United States in the 1920s, it has mainly been found in New England and the mid-Atlantic states. It was first found in New Hampshire in the year 2000 in Portsmouth. Today, infestations have been recorded in more than half the towns in the state, and in nearly every county.
Hemlock is a commercial wood, though not as popular as other conifers such as pine and spruce, and its bark is a common landscaping mulch. It also has value as a food source for wildlife who eat the seeds dispersed from its cones, and as habitat, because hemlock stands tend to grow thickly together. They also are associated with erosion control.
“If you lost the hemlock, you’d lose a significant and important tree,” Hunter said.
The N.H. Division of Forests and Lands has been tracking woolly adelgid infestations and has written an action plan for addressing the issue. For more information, visit www.nh.gov/nhdfl/.
All possible sightings of suspect infestations in uninfested counties must be reported to the Forest Health Program at 464-3016. Infestations in already infested counties should also be made to the Forest Health Program in order to track the spread. Infested nursery stock should be reported to the Division of Plant Industry at 271-2561.