Predator beetles released on Lake George to eat hemlock-killing bug

By Gwendolyn Craig

Surveyors are finding more areas along Lake George have the invasive bug that kills hemlocks, and treatment options, including the release of a non-native predator beetle, have begun.

A camper reported sick hemlock trees at the Glen Island Campground earlier this summer and the state Department of Environmental Conservation later confirmed the presence of the invasive hemlock woolly adelgid. DEC, in partnership with several organizations, have identified 250 acres of infected trees, but that number appears to be increasing.

The Nature Conservancy confirmed last month that the invasive bug has infected hemlock trees on Dome Island, a protected area owned by the conservancy. The DEC said Friday that surveys have identified more adelgid-infected trees near Pilot Knob, a hamlet on the south eastern side of the lake.

“So far that infestation looks small, though there is additional survey work needed to better determine the size,” a DEC spokesperson said.

Treatment of the trees has begun, with DEC using two kinds of pesticides that kill the woolly adelgid. One, called dinotefuran, “is fast acting and typically starts killing HWA (hemlock woolly adelgid) throughout the tree within weeks,” the spokesperson said. The second pesticide, imidacloprid, is slower to show results, “but its protection lasts up to seven years.”

But there are other methods at work.

Mark Whitmore, an entomologist and leader of the New York State Hemlock Initiative, released 620 beetles at the end of October called Laricobius nigrinus. The beetles are predators of the hemlock woolly adelgid, but are originally from the Pacifict Northwest.

Whitmore breeds the beetles in his lab at Cornell University. He has been part of releasing them at more than 20 sites across the state, and now Lake George is added to the list. Whitmore can do this through a permit with the U.S. Department of Agriculture that allows for the release of biological controls.

The DEC does not need to provide permission for the beetles’ release. The DEC, however, does help fund Whitmore’s work through the Environmental Protection Fund.

In order to release the predator beetles, there has to be enough woolly adelgid for them to eat. It will take time for the beetle population to establish. Whitmore plans to return in the spring and release two more predators to the hemlock woolly adelgid, species of the silver fly. Those, too, are from the Pacific Northwest and reared in Whitmore’s lab.

“We’ll come back and we’ll keep releasing because this is basically the coldest place in the state where we have hemlock woolly adelgid right now,” Whitmore said. “We need to see if they (the predators) are successfully establishing and spreading.”

The state is hopeful that the combination of treatments will work for Lake George.

“These particular biocontrol methods for HWA have been extremely vetted both federally and by universities over the years,” a DEC spokesperson said. “DEC will continue to monitor the success of any biological control efforts throughout New York.”

For now, we wait.