Woolly adelgid spreading on Signal

Signal Mountain officials fear that the woolly adelgid is moving into the town’s hemlocks, specifically in the Shoal Creek area. At the Signal Mountain Town Council’s January work session, officials discussed what should be done to save the town’s hemlocks.

“Some of the trees are probably not accessible, but at least we could try to protect some of them,” said Mayor Bill Lusk.

Town of Signal Mountain Tree Board chairman Noah Long said the woolly adelgid is a microscopic aphid-like insect that only infests hemlock trees. This is because the hemlock operates on a reverse seasonal cycle from most other trees, with its sap levels coming up in the winter and going down in the spring, he explained. The tiny bug’s lifecycle is similar — thriving in the fall and winter — and thus inhabits the hemlock trees, he said.

Susan Robertson, the town’s vice mayor and former Tree Board liaison, said the woolly adelgid is often carried by birds who hop from tree to tree. While the invasion is still mainly in Walden, it will inevitably reach the hemlocks in the town of Signal Mountain, she said.

The Council discussed partnering with the Tree Board and possibly even Walden to find a solution. Long said he would like to have a forester come up the mountain to “cruise the timber” and survey the land in order to estimate a possible cost for treatment.

Injecting a single tree can cost around $200, he said.

“Right now they are saying treatments seem to be effective up until five years,” said Long.

Treatment options include injecting each individual tree with a chemical or putting the chemical in the ground at the tree’s base so it can seep into the roots. The chemical used to treat the trees, however, can harm aquatic life, so it’s not safe to pour into the ground surrounding trees near a creek or body of water, such as those in Green Gorge.

If the town decides to treat the trees itself, donations and volunteers to get the job done would most likely be involved, Long said. Town officials said they will continue to discuss with the Tree Board the best course of action.


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