Most people who are interested in eastern North American forests are all too aware of the woolly adelgid.  This little critter was introduced from Asia sometime in the 1940’s (possibly earlier).  It didn’t become a significant problem until thirty years ago.  At that time major infestations were recorded in the Mid-Atlantic area; in the ensuing decades it has relentlessly spread along the Appalachian Mountain chain, with all of the Connecticut counties recording it for over twenty years.  Adelgid can kill a full grown hemlock in under five years.  The eggs and the insects easily travel from one stand to another on the wind, or by birds, deer, and other contact, especially human activity.  It is aided in its destruction by the presence of elongated scale, also an Asian invader, which doesn’t kill the tree outright, but substantially weakens it.  The increase in scale probably goes along with the increase in adelgid.

The only completely effective controls currently are some of the nasty insecticides, or if the entire tree can be reached, horticultural oil spray which suffocates the eggs.  Some biological control through the introduced predators of the adelgid is also possible.  But the predators are hard to bred and do not survive well in all areas. *  Thankfully, in northern areas (and just barely Connecticut) extremely cold, dry winters can substantially reduce infestations of adelgid, though not of scale.  However, in much of the Applachian range, the hemlock is going to become much rarer, if not locally extinct.**

All of which means that keeping a close eye on the hemlocks is very important.  For better or worse, Esperanza’s landscaping relies heavily on this tree.  Last year, the big trees were treated with insecticide and the smaller trees with oil.  Technically I ought to have the tree company come every year.  But, finance rules, and this year’s tree budget (we try for Balanced budgets around here, not being a government) is earmarked for the Japanese maples.  Although, I probably will spray the small trees myself.  I am reasonably happy with this decision, because while inspecting the hemlocks today, I found only one set of trees that clearly had adelgid.  It was probably brought in one someone’s clothes, or by a deer or bear, as the infestation was primarily on branches of the same height, weaving through the stand.  It looks quite pretty, by the way, when a branch is heavily infested with eggs: sort of like little white pearls or cotton balls at the base of every needle, a bit like artificial snow sprayed on a winter diorama.  These branches were clipped off and put in the trash.  Hopefully, we caught it in time. 

Now if I could only train a squirrel to check the tops…

*one is also, of course, introducing another alien…which tends to have unexpected problems…

**Ironically, it probably was originally a much less common tree in southern New England and farther south before the nineteenth century.  It was never a popular lumber tree, which meant it was left, and its seedlings could compete in the second or third growth forests easily, as it will grow in both sun and deep shade.