CARY -- The town is mounting a defense against a tiny insect that has plagued hemlock trees from Georgia to New England and now threatens a small outpost of the trees in Hemlock Bluffs Nature Preserve.
The hemlock woolly adelgid, an insect like an aphid that is native to Asia, has been found in 11 of the preserve's 235 Eastern hemlock trees so far and could wipe out the population if left unchecked.
The insect kills trees by feeding at the base of the needles, which eventually turn brown and drop off.
The town is working with state, federal and private tree experts to develop a plan to combat the woolly adelgid. Options include injecting pesticides into the trees or around their bases or spraying the trees with special soaps or horticultural oils.
The Eastern hemlocks in the 158-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 state owns most of the land in the preserve, which is operated by the town and draws about 100,000 visitors a year.
This is the first time the woolly adelgid has been found in the preserve, said Doug McRainey, parks planning manager for the town. McRainey said the insect could have come to Cary on hemlocks used in landscaping.
"Hemlocks are sold at nurseries and garden shops, so they can find their way," he said. "We knew it was just a matter of time."
The hemlock woolly adelgid arrived in the Western United States in the 1920s and first appeared in Eastern states in 1951. The insects do relatively little damage in Asia, in part because of natural enemies and resistance in trees.
Hemlocks in the South appear to be more vulnerable, dying within a few years of an infestation, compared to a decade in the Northeast, according to a study published last year. One theory is that cold winters may slow the adelgid's progress.
Hemlock Bluffs Nature Preserve remains open, though it will likely close on days when treatment takes place. In addition, the town plans to conduct a "hemlock health census" to map all the Eastern hemlocks in Cary and determine which ones are infested with woolly adelgid.
Town officials expect to keep the insects in check but aren't confident they'll ever be able to get rid of them.
"The goal is eradication," McRainey said. "But I think we're resigned to the fact that this is going to be an ongoing effort."
