Left unchecked, the Hemlock Wooley Adelgid, Asian Longhorn Beetle, and the Emerald Ash Borer would just about wipe out one-third of the trees in North America. Imagine the scene, something out of a sci-fi movie. Just stubs of billions of dead trees across the Southern Tier, and beyond. In today’s column, I will give you some insight into these three little critters that have already, and continue to destroy our forests. First the Adelgids.
They are aphid-like insects. The hemlock woolly adelgid (HWA) is a tiny exotic invasive species that gets its name from its woolly white appearance and because its host is the hemlock tree. Adults lay 50-300 eggs that are wrapped in a white fluffy substance secreted by an adult female. Nymphs hatch from the eggs and use their mouthparts to pierce and suck sap from the hemlock branch. These nymphs go through several stages before becoming adults and then wrap themselves with a white, fuzzy covering. Some adults stay on and suck sap from young twigs on hemlock trees, others fly off to find another tree. They cause the hemlock needles to dry out and drop. The defoliation of the tree can cause the hemlock to die in only a few years.
The Adelgid is native to Asia and was accidentally introduced to the West Coast in the early 1900's, and later to the Virginia area on the east coast around 1950. It arrived by importing Asian species of hemlocks (which are resistant to the HWA) and took a particularly fond diet of the Eastern Hemlock and Carolina Hemlock (which are NOT resistant to the bug).
This insect now infests about one-half of the native range of hemlock in the eastern United States. In Virginia, New Jersey, Connecticut, and portions of Pennsylvania extensive tree mortality and decline are common. Here in NY, the first discovery of the HWA was in the Hudson Valley in the 1980s, the insect has spread north and west to the Catskills, the Capital Region and even the Finger Lakes and other parts of western New York. Currently 25 New York counties are infested with the HWA. This insect will have a long-term adverse impact on hemlock forests and associated habitats for many wildlife species. The entire range of eastern hemlock may become infested within the next few decades.
What can we do? First, learn how to identify the hemlock woolly adelgid. Report it to the DEC if found. Help with conduct surveys in your in the area through groups like the NYS Forest Owners Association and Cornell Cooperative Extension. Look for the hemlock woolly adelgid on hemlock needles, especially on hemlocks that look stressed and are losing needles. The adelgid looks like snow on the branches of hemlocks, easily spotted against the dark green needles. Report findings to the DEC on the volunteer survey form found at: www.dec.ny.gov/animals/7250.html. Treatments of large trees are very difficult, small trees in landscape settings can be sprayed with insecticidal soaps or horticultural oils (which are non-toxic). They kill the infestation by smothering it, much the way we use dormant fruit tree oil sprays on apple trees to kill aphids.