Battle continues with tree-killing insect
By Scott Nicholson
The beetle battle is continuing as foresters and scientists try different techniques to turn the tide against the hemlock woolly adelgid.
The Blue Ridge Parkway is currently seeking public input to identify issues and additional study during an environmental assessment for control strategies against the invasive pest.
Parkway officials and National Park Service biologists believe a long-term management strategy is needed to preserve hemlock forests, which play a vital role in shading streams and making them cool enough for native mountain trout.
Chris Ulrey, a regional forester with the park service, has been fighting the non-native adelgid for years.
“It’s hard to find a hemlock anymore that doesn’t have it,” he said. “We’re using biological controls and predatory beetles as we can, but we’re not really saving trees that are already infested. In the short run, we’re using chemical techniques and have used soil injection for the last four years.”
Even a chemical-pesticide approach needs good conditions and time to be effective.
Ulrey said the dry spring has hampered protection because the root systems draw nutrients and applied chemicals from the soil after a rain.
The chemicals have also not proven to provide permanent protection, as Ulrey said biologists now find they have to again treat trees that were first treated four years ago because the pest has returned.
Dr. Richard McDonald, known locally as “The Bug Doctor” because of his research with permaculture and beneficial insects in gardening, said a type of ladybug brought in from places where hemlocks have a natural protection will be the ultimate key for restoring natural balance.
McDonald has been conducting research on a predator beetle, Laricobius nigrinus, that preys on the hemlock woolly adelgid.
McDonald has been conducting experiments at Hemlock Hill, near Lees-McRae College in Banner Elk, for four years and says his data shows the Asian beetles are an effective antidote to the hemlock pest.
“There’s a giant crunching sound on Hemlock Hill and that’s adelgids being eaten by the millions,” he said, reporting that good data has come from the study and shows the beetles are a clear answer to the problem, which he characterizes as part of an ongoing natural struggle in the forest “that goes on whether we see it or not.”
McDonald and his fellow researchers have also shown that infested trees can recover through the natural cycle of their needles. He said he wasn’t against the use of chemicals, but said the predatory beetles were a more permanent solution that mimicked the type of checks and balances in the Pacific Northwest, where similar species of hemlocks have resisted damage from the adelgids.
“This is nothing more than ladybugs versus aphids,” McDonald said. He also acknowledged that instead of fighting to save big trees that were severely infested, it might be better to focus on areas where the hemlock woolly adelgid has yet to deeply sink its fuzzy feeders.
“It’s a battle of numbers,” McDonald said. “If I had a billion of these beetles and released them, the battle would be over. The hard part is getting enough beetles.”
Ulrey also predicted the adelgid numbers would eventually crash as the beetles gained in population and region, and echoed McDonald’s belief that the hemlocks would likely be back in balance within five to seven years.
“We don’t have to worry about a full-on extinction,” Ulrey said. “But we’ll probably see some local extinction.”
The park service has been focusing on treating hemlocks around the Simms Pond and Cone Park areas on the parkway. “We’re not sure how many we’ll be able to save,” Ulrey said.
McDonald said the public can play an important role by calling state legislators and park service officials and supporting a widespread use of beetles and the provision of resources to release them.
Written comments for the Blue Ridge Parkway’s Environmental Assessment can be mailed to Blue Ridge Parkway, Attn: Suzette Molling, 199 Hemphill Knob Road, Asheville N.C. 28803 by July 2.