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Beetles released to attack invasive species

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Beetles released to attack invasive species | Dec 7th 2012 1:00 AM
Friday December 7, 2012


Staff Writer

POWNAL — About two millimeters long and appearing as black specks, the town’s newest 379 residents are here to hopefully stay and perhaps eat a few unwelcome newcomers.

On Thursday, two people from the Department of Forests, Parks, and Recreation released nearly 400 laricobius nigrinus, (Small black beetle) onto four hemlock trees on Mason Hill Road, near the Massachusetts state line and next to a tributary to the Hoosic River. Jim Esden, forestry specialist for the department, said he hopes the adult beetles will survive the winter and feed off the hemlock woolly adelgid, an aphid-like insect that has been spreading slowly northward


and was reported in Pownal over the summer.

Hemlock trees

The adelgid is an invasive species and threatens the health of hemlock trees, said Esden. The small black beetle, a native of the Pacific northwest, eats nothing but adelgids and follows a similar life cycle, being active in the winter when it is not too cold and remaining largely dormant in the hot summer. Esden said chemicals can be used to kill adelgids, but biological controls have their advantages.

“Because this is a water supply area, we didn’t want to use chemicals,” Esden said.

The four hemlock trees sit off Mason Hill Road on property owned by Williamstown, Mass. Esden said the water source serves as an emergency supply for Williamstown, making the chemical option less than desirable.

Esden said while chemicals act fast and can offer some lasting protection, if these beetles survive the winter and breed they will work indefinitely and spread along with the adelgid. He said he does not expect the beetle will wipe the adelgid out, but will keep the population from growing to the point where the hemlocks are noticeably impacted.

Barbara Burns, forest health program manager for the department, placed about 100 beetles on each hemlock tree, which were selected for their health and adelgid infestation. She said the beetles need enough adelgids to eat, otherwise their population will not take hold. She said the beetles released Thursday were grown in a lab by Virginia Tech, Va., however their ancestors are from Idaho. They came in small tubes, roughly 100 beetles to a tube, and were gathered on white shreds of paper for placement onto each tree.

Esden said the beetles only eat adelgids and nothing in this area specifically preys upon the beetles, so the odds are fair they will not all be eaten by spring. He said this same type of thing was done three years ago in Windham County, but it that is not enough time to tell if the beetles are working. He said their use has been documented in the past and shown to work, and while they are slow to take effect, the spread of the adelgid is not fast, either.

According to Burns, the beetles’ presence in Pownal is the first time they have been seen in Bennington County. They were found by volunteers working through a survey program the state runs and their most visible form is a white, waxy substance that appears on the needled branches of hemlock trees. The adelgids produce this material as they feed on the plant’s fluids.

“We have several acres of infested trees that we know of,” said Burns, adding that she or someone from the forest department will return to the Mason Hill site in about a year to see how things are going.

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Written by vaphc

December 13, 2012 at 9:12 am

Posted in Insects, Science, Trees

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