SALT POND MOUNTAIN — On Friday a Virginia Tech research team working to stop destruction of Appalachia’s iconic hemlock trees unleashed a new microscopic weapon in the fight against the tree-killing woolly adelgid.

Tech entomology professor Scott Salom and graduate student Katlin Mooneyham seeded infested hemlocks on private property near Mountain Lake in Giles County with about 1,000 laboratory-grown eggs of the Laricobius osakensis, a newly discovered beetle species from Osaka, Japan, that preys almost exclusively on the woolly adelgid.

The project site sits on a high slope with good sun exposure and low temperatures and is home to some of the healthiest hemlocks Salom said he’s seen in a long time.

Snow that fell on the mountain earlier in the week still lay on the ground beneath the trees, and fingers grew quickly red and numb in the cold. Meanwhile, 40-degree temperatures were forecast for the bottom of the mountain.

Salom hypothesized that the lower temperatures and higher precipitation on the mountain may hurt the adelgid but help the trees.

The team hopes the new beetle species (nicknamed “Larry” by the lab staff) will give the trees another ally in their fight for survival. If the project is successful, the beetle species could populate the eastern forests and help save hemlocks throughout their eastern range.

Two of the world’s nine hemlock species grow in eastern North America, the eastern hemlock and the Carolina hemlock. The native range of the eastern hemlocks stretches from New Brunswick, Canada, in the north, south to Alabama and west to Minnesota. Since the late 1980s, both tree species have been decimated by the woolly adelgid.

Although the hemlocks have little commercial value, Mooneyham said their importance lies in their cultural and ecological value.

“People are used to seeing the hemlocks, and they love them,” she said.

Furthermore, the hemlocks cool the forest floor in the hottest parts of the summer and provide cover for birds and other animals in winter, she said.

Hemlocks also cool streams and rivers, boosting the health of aquatic species. Scientists warn that widespread loss of the species would have grave consequences for the eastern forest ecosystem. The adelgid is the primary killer.

Introduced to the U.S. from southern Japan before 1951, the adelgid had no native predators in the eastern part of the country, and the native hemlock trees had no defenses. Since it was first identified in Richmond in 1951, the adelgid has spread rapidly.

The adelgid deposits its eggs in a white “woolly” case on the underside of young, healthy hemlock twigs. After they emerge , the insects pierce the bases of hemlock leaves and suck sap and nutrients from the tree, eventually killing it.

About 19 percent of the hemlock trees in Southwest Virginia have died from adelgid damage, and all hemlock trees across the state are believed to be infested, according to Russ MacFarlane, silviculturist for the George Washington and Jefferson National Forest.

In 2005, the Forest Service was forced to cut about 500 dead hemlock trees along Giles County’s Cascades Falls trail, said Barb Walker of the Forest Service’s Blacksburg office.

The dead trees posed a falling hazard to users of the popular Cascades Recreation Area, Walker said.

While some pesticides such as the neonicotinoid imidacloprid do save hemlocks from the adelgid, widespread chemical treatment of hemlocks in forests across their eastern range is impractical. Biological controls, such as the introduction of natural predators that can thrive here, is thought by scientists to be the only long-term solution.

Salom has worked on the adelgid problem for about 15 years, mostly by researching the insect’s predators, which are found in Asia and in the western United States. His team is the first to work stateside with Laricobius osakensis, in a project funded by the U.S. Forest Service. Salom cooperates with a team at the University of Tennessee that is also growing the beetle in the laboratory.

Salom’s team has worked successfully on another Asian beetle species that eats the adelgid, called Laricobius nigrinus. But the new beetle, Laricobius osakensis, may be particularly effective because its life cycle closely matches that of the adelgid.

Furthermore, Salom said, the new beetle feeds during winter, when the adelgid is also active. The beetle lays one egg inside the adelgid’s woolly egg cases, which can contain hundreds of the insects’ young. When the beetle larva hatches, it can eat hundreds of adelgid young. When it runs out of adelgid young, Salom said the beetle preys on adult adelgids.

Theoretically, one Laricobius osakensis beetle could impact up to 3,000 adelgids, Salom said.

Combined with other adelgid predators, the new beetle may help ensure survival for the remaining eastern hemlocks.

That’s the hope, but there are still obstacles.

Salom’s team will monitor the Giles County project area for a few years to determine if the beetle is thriving, but more importantly to find out if the adelgid population is decreasing.

The team is introducing the beetle into a similar site in West Virginia, and will monitor its effect there as well.

To make a lasting impact, Salom said, the team must also work out an efficient way to breed the new beetle in mass quantities in the laboratory, and determine the most effective way to introduce it into eastern forests.

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