Hemlock needles have two white lines on the undersides. The hemlock woolly adelgid can be difficult to spot because of its tiny size, but the cottony egg mass is the main indication you should look for on needles, according to officials. An electron microscope image of the insect is shown inset. (DEC, USDA photos)
SCHENECTADY COUNTY An invasive insect that feeds on hemlock trees has been discovered for the first time in Schenectady County.
The state Department of Environmental Conservation confirmed Tuesday that a hemlock woolly adelgid infestation was located in the yard of a home in the city of Schenectady on Aug. 20. The tiny insect, which comes from East Asia, attacks forest and ornamental hemlock trees and can cause widespread damage.
First discovered in New York state in 1985, it has now been detected in 28 counties, in addition to Schenectady, according to the DEC. The pest was discovered in Albany County several years ago and in Schoharie County in 2011, but has primarily been concentrated in the lower Hudson Valley and the Finger Lakes region.
At a glance
The Department of Environmental Conservation offers the following management strategies for homeowners and woodlot owners who have hemlock trees infested with hemlock woolly adelgid:
• Reduce hemlock tree stress by watering during drought periods and pruning dead and dying limbs and branches.
• Avoid the use of nitrogen fertilizers on infested hemlocks, as it will actually enhance HWA survival and reproduction.
• Be cautious while moving plants, logs and mulch from infested to uninfested areas, particularly when HWA eggs and crawlers are present from March through June.
• Move bird feeders away from hemlocks and remove isolated infested trees from woodlots to help prevent further infestations.
• Spray hemlock foliage, on trees small enough to be saturated, with properly labeled horticultural oils and insecticidal soaps.
• Systemic insecticides, applied around the base of the tree or injected into the trunk, may be an option for larger trees. For insecticide guidelines for New York, see Cornell University’s Crop and Pest Management Guidelines at http://ipmguidelines.org and consult a certified pesticide applicator.
• In a woodlot, unless timber revenue is the main objective, pre-emptive cutting of uninfested hemlocks is not recommended. Woodlot owners should seek advice from a DEC forester by calling the DEC’s toll-free Forest Pest Hotline at 1-866-640-0652.
• For questions or to report possible infestations, visit DEC’s website at www.dec.ny.gov or call the Forest Pest Hotline.
In addition to New York, the DEC said 17 states along the Appalachian Mountain range, from Maine to Georgia, have reported infestations.
The tiny insect is difficult to see with the naked eye, but clearly announces its presence with small, white, woolly masses called ovisacs that can be found attached to the underside of a hemlock’s twigs, near the base of the needles.
A contractor working on the Schenectady property where the insect was identified saw an infested twig that had fallen onto the roof of a shed and suspected the insect was present, DEC spokeswoman Lori Severino said. Severino estimated the insects had been in residence at the undisclosed city location for one to two years.
Trees in the surrounding area will be inspected during fall and winter, she said.
The tell-tale white masses that signal an infestation are smaller than the head of a cotton swab, but easy to spot, said Wayne McCormick, president of Earth Care Plus Inc., a tree service in Ballston Spa. McCormick, a certified arborist, has worked in the Philadelphia area, in Bergen County, NJ, and in Westchester County, where he saw firsthand the damage the insect can do.
“It was a huge problem,” he said. “Basically, if you had hemlock trees and were not treating them, you were going to have problems with hemlock woolly adelgid.”
The insects feed on young twigs, causing needles to dry out and drop prematurely, which in turn causes branch die-back. They spread primarily during their first life stage — the crawler stage — as a result of wind or animals that come in contact with the sticky ovisacs and crawlers.
Infestations can also pop up in new locations when infested wood is moved.
Once an infestation takes hold, if left unchecked, a tree’s decline typically lasts from four to 10 years before it dies completely, according to the DEC.
“It is very aggressive, and it will defoliate hemlock trees, and unfortunately with conifers, once the needles are dead, they’re dead. They don’t refoliate, so it really has a major impact on these trees if you don’t catch it soon enough,” McCormick said.
The good news is an infestation can be controlled even if caught after damage becomes noticeable.
“You can control it pretty easily with just a horticultural oil, which is a registered pesticide, but fortunately, it’s non-toxic. It’s not a chemical by any means. It’s a suffocating agent,” he explained.
Once the pests are discovered, a maintenance program is often needed to keep them at bay, he noted.
“You typically need to be treating these things sometimes multiple times per year for years on end just to keep it from outbreak,” McCormick said.
Biological control methods, which incorporate natural predators, are also being researched and introduced throughout infested regions, the DEC reports. There are no resistant hemlock varieties, Severino noted.
“Some live longer than others, but the differences are likely environmental conditions in the area of the tree,” she said.
The dry conditions the Capital Region has seen this summer have stressed trees and made them more susceptible to pests like the hemlock woolly adelgid, McCormick said. Hemlocks are often planted in a monoculture, which encourages insects that feed on the trees to take up residence in large numbers.
“People have a row of them, many of them in the same area, and it just turns into a haven,” he said.
McCormick recommended planting coniferous trees like firs and spruces in addition to hemlocks, to prevent creating a setting where hemlock-loving insects will thrive.
More information about the hemlock woolly adelgid can be found at www.nyis.info.