First Adelgid Sighting
Marcia reports that she found the first sign of hemlock woolly adelgids in Plummer’s Hollow a couple days ago: remanants of the woolly masses on the undersides of a few twigs on a hemlock tree along the Ten Springs Extension Trail above the Big Pulloff — i.e., less than a half-mile from the bottom. This is what we’ve been dreading for some time now, as we’ve watched the adelgid wave move toward us from the southeast, where some of the best-known old-growth remnant stands, such as The Hemlocks Natural Area and Sweetroot Natural Area, have been destroyed. Adelgids have already established themselves north of us in the Rothrock State Forest, so we knew it was only a matter of time.
Though doubtless the northeast-facing slopes of Plummer’s Hollow were covered with old-growth hemlock two hundred years ago, now only a remnant population of second- or third-growth trees numbering in the low hundreds hangs on in the deepest parts of the hollow. This may be to our advantage, though, in slowing the advance of the adelgids — some reports indicate that hemlocks in rich, mixed conifer-deciduous forests hold out longer than those in pure stands. We are, of course, hoping against hope that a biological control will take hold. Insecticides aren’t effective against the adelgid, and in any case we wouldn’t allow their use even if they did work — overall biodiversity has to take precedence.
We’re in the middle of a cold snap right now, with nighttime temperatures hovering just above zero F, and needless to say we are cheering the cold on. We’d welcome temperatures ten or even twenty degrees colder than that, despite the inconveniences that might cause us. The loss of all mature hemlocks in Pennsylvania, while not catastrophic for the species as a whole, could have a devastating effect on forest ecostystems, especially cold-water fisheries.