Researchers introduce bug, hoping to kill hemlock pest
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By SUSAN SMALLHEER Rutland Herald Staff - Published: October 27, 2009
BRATTLEBORO — Hundreds of little black beetles from Idaho were released into a stand of infected hemlock trees in Brattleboro last week, in a move that state officials hope will ultimately save millions of trees from the hemlock wooly adelgid.
Laricobius nigrinus, native to the Pacific Northwest and also known as tooth-necked fungus beetles, were released by a graduate biologist from the University of Massachusetts in Amherst, but only after studies by the federal Department of Agriculture determined the beetles wouldn't become pests themselves, said Jon Turmel, state entomologist with the Agency of Agriculture.
According to Turmel, the USDA studies showed that the beetle only eats the wooly adelgid. The beetle feeds on all live stages of the adelgid, making it a particularly valuable tool.
Hemlock wooly adelgid, which has killed millions of hemlock trees primarily in the southern United States, first showed up in Rockingham more than two years ago. Since them, the insect has been located in Brattleboro, Vernon, Guilford, Jamaica, Townshend and Dummerston, all in the state's southern tier.
The wooly adelgid sucks the sap of the hemlock, an important forest shade tree for deer yards, eventually leading to its death.
But state and federal officials believe that northern New England's cold winters may also be a big help in combating the adelgid, which itself was an introduced insect from its native Asia, according to the U.S. Forest Service's Web site.
The Idaho beetles were released into the largest hemlock stand in the state known to be infested, said Jim Esden, a forester with the state Department of Forests, Parks and Recreation.
The UMass researcher, Dave Mausel, has also been releasing the beetle in Massachusetts, Connecticut and Maine, Turmel said, as part of a research project.
Esden, who said he wasn't in Brattleboro for Friday's release, said it was timed to when the beetles could be collected in Idaho, sent to Vermont and released under the right conditions.
The strain of the Idaho beetle is believed to be more cold-tolerant than other members of the Laricobius nigrinus family found in more temperate sections of the Pacific Northwest, Esden said.
Esden said the beetles were released on land owned by Cersosimo Industries, a large lumber operation.
Esden said that the adelgid is believed to be primarily spread by wind and birds. While the first infected tree was located in Rockingham, a short distance from the Connecticut River, no other infestations have been found in Rockingham.
Such is not in the case in the southernmost towns, Vernon, Guilford and Brattleboro, and the insect has spread to Dummerston, and the West River towns of Jamaica and Townsend.
Esden said that research and anecdotal evidence show that the cold has a strong effect on the wooly adelgid, which looks like tiny bits of cotton or white wool on the underside of the hemlock when infected.
He said that while the wooly adelgid has been identified in Massachusetts for 17 years, there are no known deaths of hemlock trees in that state.
"We think the winter weather is helping us," he said. Researchers at the University of Vermont are also doing research on a fungus that attacks the adelgid, he said. "We're hoping to add some downward pressure on adelgids."
The longer the hemlock takes to succumb, the longer researchers will have to find an effective way of combating the insect.
Hemlock woolly adelgid was introduced from Asia into the Pacific Northwest in 1924. It was probably introduced into the northeastern US in the 1950s. The insect has been damaging hemlock ever since, and it continues to spread.
According to the U.S. Forest Service's Web site, in the Northeast, Hemlock woolly adelgid can have two generations per year. All populations are made up of females that reproduce asexually.
The U.S. Forest Servicesays the biggest losses of trees have occurred in Virginia, New Jersey, Pennsylvania and Connecticut.
In Vermont, the hemlock comprises about 17 percent of the state's trees, according to state officials. The eastern hemlock is an important ornamental plant, in addition to being a mainstay of the state's forests, and there are 274 different eastern hemlock cultivars.
susan.smallheer
@rutlandherald.com
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