Elongate hemlock scale discovered in NH forest
USDA Forest Service, Northeastern Area State and Private Forestry
271 Mast Road, Durham, N.H.
May 16, 2008
DURHAM, N.H.—A tiny invasive insect found in the Middle Atlantic States and southern New England has spread to New Hampshire.
The elongate hemlock scale (EHS), or Fiorinia externa, is a native insect of Japan. The insect is considered invasive in the United States. Its feeding weakens and kills dozens of conifer tree species.
The one to two-millimeter-long insects prey on 43 species of coniferous trees, including 14 native species of eastern and Carolina hemlocks. Fir and spruce trees are even more susceptible to the EHS than hemlocks.
In the East, the EHS earlier ranged as far north as Massachusetts. It can be found as far south as Virginia and as far west as Ohio.
State forest health managers said they were not expecting the EHS to arrive in the state so soon.
“We were surprised,” said Kyle Lombard, the forest health program coordinator for the New Hampshire Division of Forests and Lands.
“It’s been in those southern states for fifty years. We expected our winters here were cold enough that it would stay south of us. I’ve read reports recently, though, indicating the EHS appeared to be adapting to a colder climate.”
Lombard said Forest Health Specialist Jen Weimer spotted the EHS infestation earlier this month in Milford while on a routine hemlock woolly adelgid (HWA) service call. A resident called their forest health office saying they thought they found an HWA infestation. When she went out and confirmed the infestation, Weimer also noticed the EHS infestation, Lombard added.
Lombard said it is common to find EHS and HWA infesting the same trees. “Their vectors are the same,” he said. “They are dispersed mostly by birds and wind. We always find adelgid near water bodies. When moved by birds, both the scale and adelgid often end up near water bodies. They found the recent EHS infestation by a home in Milford, on the edge of a pond by a beaver dam.”
The Milford EHS infestation is scattered throughout the two-mile radius wherever hemlock is found, said Lombard. “We’re estimating it’s been there three years,” he said.
Lombard added that the combined HWA and EHS infestations will kill infested trees quicker than they would have done otherwise. “This new infestation will worsen the HWA problem hemlocks are already facing. Most of the hemlock mortality down south occurred when the scale joined the adelgid on the same tree,” he said. “This certainly puts a lot more hemlocks in southern New Hampshire at risk.“
Lombard indicated the larger the infestation, the more difficult it is to find a solution.
“If we can find an outbreak of scale when it’s still small, say 50 trees or less, it’s easy to control with pesticides. When it’s a larger area, we need to find biological controls to slow down its spread.”
He added that the Hollis infestation is already considered a larger one which will require biological controls. Fortunately, control resources are available through the State’s partnership with the U.S. Forest Service.
“Those beneficial insects and diseases that are controlling scale in other parts of the country just now need to be brought to New Hampshire.”
Lombard said he is asking residents to keep an eye out for the HWA and EHS in their areas. “If you find a population at a low level you can control it quickly and easily.”
He said people who spot what appears to be HWA or EHS on hemlock trees in their area can notify the Division of Forests and Lands Forest Health Office at 603-464-3016.
On the Net: Elongate Hemlock Scale Pest Alert (Northeastern Area, State & Private Forestry) http://www.na.fs.fed.us/spfo/pubs/pest_al/ehscale/ehscale.htm
Photos can be found at http://www.na.fs.fed.us/nanews/archives/2008/archives08.shtm
Return to nhbugs.org.