Forest Pests

Do you see any signs of invasive pests damaging trees?

Smooth, pale gray bark is a distinguishing feature of a healthy beech tree. In this beech grove, notice the many beeches with blemished, blistered bark that indicates the presence of beech bark disease. This deadly damage is caused by a double whammy – an invasive scale insect wounds the bark enough to allow Nectria fungus to penetrate the tree.

If you look further down the trail, you’ll see a struggling ash tree also suffering damage from an invasive pest. The emerald ash borer is an insect that devastates ash trees when its larvae tunnels under the ridged bark to the part of the tree that stimulates growth. Signs of infestation include canopy leaf loss, blonding of bark, and lots of woodpecker activity. Losing ash trees not only hurts certain wildlife species, but also undermines the many centuries old Native American tradition of making baskets from ash as well as the more recent American tradition of using ash for baseball bats.

While the hemlocks in this forest are generally healthy, milder winters resulting from climate change have made New Hampshire hemlocks more susceptible to deadly infestation from invasive, aphid-like insects called hemlock woolly adelgids, named for the white, woolly egg masses they lay at the base of hemlock needles. Climate change has also enabled spongy moths, with caterpillars capable of defoliating trees, to survive in more northern areas.


James Frohn, “Looking for American Beech”

Emerald Ash Borer

The Importance of Hemlocks

“The Effect of Climate Change on Gypsy Moth,” May 19. 2019