Q. If I plant Canadian hemlocks that are dying in the Appalachian mtns, will they catch the wooly Adelaide?
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The hemlock woolly adelgid (Adelges tsugae) is a prominent threat to eastern (or Canadian) hemlocks (Tsuga canadensis) and Carolina hemlocks (Tsuga carolinianus) in the eastern United States. The possibility of having your newly planted trees succumb is high but depends somewhat upon your location.
The US Forestry Service has determined that there is a strong relationship between winter temperatures and adelgid persistence. Because winter temperatures fluctuate and are increasing in the northeast, however, the entire range suitable to Tsuga canadensis here falls within the area that will not impose an dependable limit on adelgid populations.
Hemlock woolly adelgids can reproduce in multiple generations per year with a single female generating up to 40,000 in a year. There are control approaches that a homeowner can take, but they require annual attention, persistence and some luck. More information on the life cycle and management of woolly adelgid in New York State can be found here.