A tiny but harmful insect has returned to trees in Cary’s Hemlock Bluffs Nature Preserve.
The town says a recent inspection of its 235 eastern hemlock trees yielded the discovery of hemlock woolly adelgids, aphid-like insects that can damage trees while feeding on their sap.
The bugs, native to Asia, were last found in the nature preserve in 2010. As it did four years ago, the town plans to eradicate the woolly adelgids by painting the infected trees with insecticide.
Cary plans to keep the park open when it treats the trees on Monday. The insecticide is harmless to healthy hemlocks, and the treatment process won’t affect park visitors.
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“The bark absorbs the paint in about 30 seconds,” said Mark Johns, a recreation program specialist for the town.
The town is encouraging residents with hemlocks to inspect their trees because the adelgids can migrate from tree to tree.
The eastern hemlocks in the 140-acre Hemlock Bluffs Nature Preserve grow along north-facing bluffs above Swift Creek, far from their normal range in the foothills and mountains of North Carolina.
The adelgids likely returned to Cary from the mountains where they’re ransacking the hemlock population, experts say.
“They’re wiping out hemlocks in the Appalachians left and right,” said Robert Jetton, an assistant professor in the Department of Forestry and Environmental Resources at N.C. State University.
The adelgids could have been transplanted by birds, deer, wind or hikers returning from Western North Carolina, Jetton said. It’s also possible that someone in Wake County purchased an adelgid-infested hemlock tree from the mountains and planted it in their yard.
The state Division of Parks and Recreation has treated adelgid-infested hemlocks at eight mountain parks since 2009, division spokesman Charlie Peek said.
The state Forest Service has treated about 5,000 hemlocks since 2007, said Rob Trickel, director of the forest health program.
“We’re doing triage,” Trickel said. “There’s too many (infested trees) to treat them all, so we have to treat the ones we can access and help the most.”
Preserving the trees is important because they provide the foundation for an ecosystem in cool, moist coves near streams and rivers.
“They create a very dense shaded environment that dictates other species in that environment … from insects to fish,” Jetton said. In the mountains, “their shade maintains stream temperatures that are ideal for trout.”
The state owns more than half the land in the Hemlock Bluffs Nature Preserve, which is operated by the town and draws about 100,000 visitors a year. The town will spend $7,130 to treat the trees.