Hemlock owners urged to keep eye out for tiny tree killer

Durham, NH—DURHAM, N.H.—The New Hampshire Division of Forests and Lands and the USDA Forest Service are urging hemlock owners to keep an eye out for signs of the hemlock woolly adelgid (HWA).

The HWA is a tiny, almost microscopic insect that feeds on hemlock trees. It is an exotic invasive insect in America and a native of Asia. The pest is closely related to aphids.

The USDA Forest Service says invasive species are one of the top four threats facing our nation’s forests. The conifer-killing HWA is considered a serious threat to eastern and Carolina hemlocks, ecologically important native tree species.

Hemlocks provide shade for rivers and streams, keeping the water cooler for native fish. The conifers also provide habitats for native animals and plants. Hemlocks are popular landscaping trees. They are found in forest stands covering about one million acres of forests in the United States.

HWA infestation is often indicated by a cottony growth on the underside of hemlock branches. Unlike most other insects, the HWA is less active during the summer and becomes more active during the winter months.

“The insects suck nutrient-rich liquid out of hemlock trees and gradually weaken them,” said Forest Service Entomologist Dennis Souto, who works out of the Forest Service’s Durham, N.H. field office. “Infected trees can die in as little as 3-5 years, especially in the South.”

Researchers first detected the HWA on this continent in Virginia in the early1950s. Over the years it spread out across much of the Eastern Seaboard.

Forest health managers detected HWA in Southern New England in the mid 1980s. Since then, it gradually spread to all six New England states. An isolated HWA population appeared on infested landscape nursery stock in 1990 in Vermont. It was quickly eradicated there and Vermont today is the only New England state that is HWA free.

State forest health managers first spotted HWA infestations on hemlock trees in New Hampshire in Portsmouth in 2000.

Kyle Lombard, the forest health program coordinator for the New Hampshire Division of Forests and Lands, said he and others have been working to control HWA spread and population size in the Granite State for the past six years. He said his agency works closely with the Forest Service to monitor, track and control the HWA population size.

”We’re trying to slow the spread of the insect. We’ve found infested trees in more than 30 towns. Wherever we spot it outside of the Portsmouth area we are eradicating it.”

Rockingham County is the HWA quarantine area for the state, said Lombard. People who want to move hemlock material must have it inspected before being allowed to transport it outside of the quarantine area.

Lombard said they use a variety of methods to keep the HWA population in check.
“We have four approved strategies. The first is what we call the ‘cultural control,’ or ‘non-chemical approach.’ We cut down and destroy infested trees.”

“Then we have biological controls. The Sasajiscymnus tsugae is a species of lady bug that eats HWA insects. We’ve had a lot of success in New Hampshire during the last five years using this strategy to reduce the HWA population.”

Lombard added, they released more than 50,000 specially bred, HWA-eating ladybugs so far in the state since 2001. “We think that’s the future of out management strategy.

“Chemical controls also work great on controlling size of the HWA population. The chemicals are actually very safe. What we’re using now is the active ingredient in a popular tick and flea control for dogs. It’s a systemic pesticide.”

“We’ve been so successful that it’s getting very hard to find any signs of infestation in Portsmouth area. We’re very encouraged with the controls so far.”

Lombard said this season they had the biggest outbreak of HWA in forested settings since 2000. “It’s quite possible the warmer winter we had didn’t kill off as many HWA insects as it usually does. In spite of this, we’re been able to control the population very well so far. “

Lombard said he thinks early detection and rapid response is the key to controlling invasive species like the HWA.

“Any pest is very treatable if you find it early. If you’re looking for the pest and you find it in small numbers, it’s very treatable. Once it gets into the forest you’ve lost it. If you think you see it, give us a call.”

People who spot HWA infestations should report any signs of the infestation to state authorities. To report infestations in New Hampshire please contact:

Kyle Lombard, entomologist
New Hampshire Division of Forests and Lands
603-271-7858
klombard@dred.state.nh.us

Outside of New Hampshire:
Dennis Souto, entomologist
USDA Forest Service
603-868-7717
dsouto@fs.fed.us

On the Net: http://www.na.fs.fed.us/fhp/hwa/