Drought makes trees more susceptible to invasive species. The NC Forest Service is fighting back.

CALDWELL COUNTY, N.C. — Our lakes and rivers are already improving from the worst of the drought, but it could take years for trees to fully recover.

Right now, they’re more vulnerable to threats like invasive species; but Channel 9 climate reporter Michelle Alfini learned that the North Carolina Forest Service is fighting back.

Towering high in this Caldwell County forest, these hemlocks have had to fight to survive, says Brian Heath with the NC Forest Service.

“It’s a very important species to our environment,” Brian Heath said before pointing to an afflicted branch. “This is a hemlock that we lost the battle on.”

The culprit: The hemlock woolly adelgid. It’s an invasive insect that latches onto hemlock branches and sucks out their nutrients.

“It just looks like a tiny white puffy cotton ball,” Heath said. “When you start having the adelgid coming in, it starts killing those lower branches and works its way up.”

Hemlocks tend to grow along stream banks, and their lower branches play an important role, providing shade and keeping the water cool.

“Better for aquatic life, trout, fish, things like that,” Heath said.

So a drought like we saw this year can leave both the trees and the environment they protect more vulnerable.

“It’s really a long-term stress occurrence that we witness, and we will see lasting impacts for often years,” said Kelly Oten, a specialist with NC State University.

Oten explained that during droughts, trees have to tap into their reserves to stay alive. In the years afterward, they need time to rebuild, so they’re less resilient to other dangers.

“Not only will the trees be less able to defend themselves against attack, but those trees are actively putting out stress volatiles that are telling pests, ‘Hey, come attack me,’” Oten said.

Fortunately, Heath says there is a way to fight the woolly adelgid.

The Forest Service uses a chemical treatment hemlocks can absorb through their roots.

“That lasts for five years,” Heath said.

Heath says it doesn’t bring back the branches that have already died, but it can slow the spread and keep trees alive long enough to help the next generation grow.

“You can almost do a 360-degree view and see the hemlocks that we saved,” Heath said.

Besides this pest, NC Extension will be on the lookout for others like bark beetles, sawflies and the emerald ash borer.

To protect trees in your neighborhood in a drought, arborists recommend using a five-gallon bucket with drilled holes to water them. Avoid fertilizing because it can dehydrate plants, and use mulch wisely because it can block water from reaching the soil.

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