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From the Forest
One Under-Rated Pest
ELLENVILLE – The white-tailed deer and campers share one thing in common: They both prefer a stand of hemlock trees for bedding in. In the winter, when snow depths accumulate above six to eight inches, deer will seek out these stands.
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The white-tailed deer and campers share one thing in common: They both prefer a stand of hemlock trees for bedding in. In the winter, when snow depths accumulate above six to eight inches, deer will seek out these stands. Hemlocks provide a natural buffer from winter’s cold winds as well as less snow to trudge through. Such areas are referred to as “wintering yards” since multiple families will congregate in these areas to save energy during winter’s doldrums. On the other hand, campers seem to use hemlock stands mostly in summer. Back when I was a backcountry ranger for the NYS DEC, it was common to find old fire-rings inside deep, dark stands of hemlock. Who could blame them? Hemlock stands serve as a natural cooler against summer’s doldrums and a “clean” place to pitch a tent. Hemlock trees cast so much shade that few plants can survive beneath them, making for a great campsite.
My own fondness for hemlock includes its proximity to water or mountain streams. When I’ve got a fishing rod in my hand, and stare upstream towards some small waterfall with a “significant other” plunge pool beneath, I am full of hope. When I see this same scenario beneath the dark canopy of hemlock, I know the water is that much more “troutable.” Brook trout depend upon cold water to survive and hemlock helps an otherwise warmer stream remain within livable limits. I also think that those beautiful red and blue spots upon “brookies” seem to contrast beautifully beneath that same dark canopy. It’s a fit for sure.
Beyond The Hemlock Woolly Adelgid
Unless, this tree’s canopy is dying back. Unfortunately, hemlock has been suffering from pest issues in the last few decades. The most well-known pest of hemlock is the hemlock woolly adelgid (HWA), introduced from Asia in 1951. HWA (Adelges tsugae) is a relative of aphids. It literally sucks the life out of trees through its needles, and trees normally succumb within two to eight years. The crown or live foliage will begin to recede and appear less full. Widespread damage from this little guy became noticeable by the 1980s, especially in the Hudson Valley. However, there is a lookalike and its damage for some reason is less familiar; maybe it’s because damage from this life-sucking insect is more isolated to southern areas of the Catskills in Sullivan and Ulster counties?
Elongate hemlock scale (EHS, Fiorinia externa) predates HWA and debuted in 1908 from China and Japan. It is located in fourteen eastern states from southern New England to Georgia and west to Ohio. In its native territory, 95 percent are dined upon by a parasitoid. However, in North America the predatory-prey dynamic isn’t synchronized, leading to some sick hemlocks. Recently, I’ve spent a lot of time in Sullivan County looking at sick hemlocks. Sullivan County certainly is well stocked with hemlock trees. In its past, Sullivan County led NYS in leather-making due to its abundance of hemlock bark used in the tanning process in the 19th Century. Although today, some sections have both HWA and EHS, while some stands merely have EHS.
EHS is more difficult to treat than HWA, which surprised me since I hadn’t previously known very much about it. EHS is an armored scale or tiny insect that also sucks the life out of the tree from the needles. It can be diagnosed by the presence of brown to dark-brown little spots on the undersides of needles, as opposed to HWA which look like puffs of cotton. Other symptoms of EHS are yellowing of needles, normally from the bottom up. Both insects cause the tree to appear lacking in the foliage department or otherwise less full.
In southern portions of the Catskills, both these insects are causing widespread damage upon hemlocks. Currently there is no feasible forest-wide treatment for these two buggers. Hopefully the future will pan out for current experiments in bio controls involving the release of predatory insects. However, on the yard-scape scale, there are chemical controls that can be taken, but this is where the two pests diverge. HWA is more easily treated than EHS since they have “softer bodies” making them more vulnerable to chemicals. HWA normally requires fewer treatments over a ten-year period. On other hand, the armored EHS is more difficult to control. Chemical treatments need to make contact when the insect is most vulnerable outside its hardened armored shell, or when the “babies” are outside crawling around. However, reproducing crawlers exist throughout the growing season making repeated treatments necessary, or the use of longer-lasting systemic chemicals that pump throughout the vascular tissue of the tree.
In any case, I’m more concerned about EHS than HWA going forward. Trees that have been treated for solely HWA have bounced back well, while those with EHS seem to lag behind and demand more attention. If your hemlock tree is looking a little bit sparse and you fail to see any white cotton-like material on the needles, carefully look for small brown markings on the undersides; It just might be elongate hemlock scale. The good news is that both these insects normally take more time (two to eight years) to cause mortality in comparison to say, the emerald ash borer, which should be treated prophylactically. For more information, visit www.catskillforest.org.
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