Recent research shows that saving hemlock trees from an invasive, fuzzy white bug is easier and less expensive than previously thought. And now, leaders in this fight for hemlocks encourage private landowners to join the renewed effort to treat and re-treat to save this iconic evergreen.
The hemlock woolly adelgid, an aphid-like insect, has killed thousands of eastern and Carolina hemlock trees in western North Carolina since its discovery within the state in 1996. In 2014, the North Carolina Department of Agriculture and Consumer Services renewed attention to the issue with its commitment of $100,000 to form the Hemlock Restoration Initiative, based at nonprofit WNC Communities. The funds prompted public and private collaborations to save the hemlock, and in 2015, the department granted an additional $250,000 over three years to continue the effort to curb the massive hemlock mortality.
Thanks to that grant, additional funds from the U.S. Forest Service and collaboration with the North Carolina Forest Service BRIDGE program and Forest Health branch, staff and volunteers treated more than 9,000 trees on state lands in early 2017 alone. They reached almost as many trees in that single season than the nine-year effort ahead of it, says Margot Wallston, coordinator of the Hemlock Restoration Initiative.
“The main message I want to get out to the public is that it is now cheaper and easier to keep your trees chemically protected,” she says. “That will ensure we maintain enough healthy hemlocks across the region to implement future complementary, non-chemical strategies without having to start from scratch.”
Holding the Hemlock High
The adelgid sucks the stored nutrients out of hemlock twigs and leads to the death of a tree species important to the western North Carolina landscape and its people. Bill Yarborough, special assistant to Agriculture Commissioner Steve Troxler, likens their deaths to “huge gray ghosts on the mountainsides.” The state’s hemlocks maintain water quality and quantity for headwater streams, of particular importance in the winter when other trees rest dormant. The evergreen shades streams for eastern brook trout, which thrive in cool waters. Hemlocks impact the nutrient cycle, keep stream banks in place and provide habitat for a variety of wildlife. Meanwhile, people share emotional and historic connections with the graceful native evergreen scattered across the rugged Appalachian range.
“As they disappear, there is no tree – native nor non-native – to fill that niche,” Wallston says.
Solutions Within Reach
The solution to curb HWA infestation requires multiple strategies working in concert to preserve and re-establish hemlocks: Chemical treatments effectively kill the insect and can halt decline, if treated or re-treated in time. Biological controls, such as the release of predatory beetles, have shown promise in reducing HWA populations by restoring a natural predator-prey balance. Lastly, researchers look at genetic options, with hopes to breed natural insect resistance for a long- term solution to save the hemlocks.
As some landowners experienced, early chemical treatments were discouraging, both expensive and extensive. But, recent research conducted in the Great Smoky Mountains National Park and published in 2016 proves that lower doses of imidacloprid-based treatments effectively control HWA. As importantly, Wallston emphasizes the research found that the chemical’s control lasts longer than previously thought. Meanwhile, cost-conscience landowners can consider lower- cost, generic alternatives of imidacloprid-based products. All lead to savings in costs to treat or re-treat in this collaborative effort to give hemlocks a fighting chance.
“The hemlock effort is a great opportunity to showcase what people can do when they work together,” Yarborough says. “There are researchers, volunteers, nonprofits, environmental groups, government agencies, municipalities, county government and philanthropists working on this project to try to make a difference. We have huge support for this program to save this iconic tree in the mountains.”