A tiny insect is posing a large threat to plants in the region, according to one West Virginia University entomology specialist.

The hemlock wooly adelgid is an insect that is a current threat to Eastern and Carolina hemlock trees and has the potential to upset entire West Virginia habitats.

“As hemlock trees are killed by this pest, the forest species composition changes,” said Daniel Frank, WVU Extension Service entomology specialist. “Not only does wildlife dependent on hemlock stands disappear, but without the cover and shade that these trees provide the temperature of streams can also change and affect native trout populations.”

Adelgids appear on hemlock branches and look like tiny cotton balls, averaging approximately 1/16 inch in length because of the white, wool-like substance they produce over their bodies. They feed at the base of hemlock needles and drain the sap causing the needles to fall off, which eventually leads to premature death of the tree.

“They may seem too small to cause any real problems, but West Virginia’s state parks and forests will be at risk for severe damage if they are not controlled,” Frank said.

The insect was first reported in West Virginia in the early nineties and can now be found in 42 counties in the state.

“The insects can be spread by birds and other animals,” Frank explains. “Additionally, they can be moved to neighboring trees by the wind.”

Frequently checking hemlocks for infestations is essential to prevent adelgid populations from building to damaging levels. Chemical control is the most common management technique. Insecticidal soap or horticultural oil sprays are used to treat small trees (30 feet high or less). However, for the treatment to work, the needles and twigs on the entire tree must be covered.

Larger trees can be treated with the insecticide Imidacloprid, which is a systemic product – meaning it can be absorbed by a plant and moved throughout its tissues. Systemic insecticides can be applied as a soil drench, soil injection or tree injection.

“Systemic products can take time to be absorbed by trees, but can be present in plant tissues for several years following application,” Frank explains. “However, trees will continually need to be re-treated for lasting control, which can become costly.”

Species of predatory beetles may provide a solution to limit future hemlock wooly adelgid destruction. The West Virginia Department of Agriculture has released and monitored beetles as part of a hemlock wooly adelgid survey and suppression program since 1999.

“We don’t have proof that using beetles to control hemlock wooly adelgid will work long-term,” Frank said. “Though, it could be a very hopeful development.”

For additional information on other pest and control options contact your local county office of the WVU Extension Service or visit anr.ext.wvu.edu/pests.



CONTACT: Cassie Waugh, WVU Extension Service
304.293.8735, Cassie.Waugh@mail.wvu.edu

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