Attack of the hemlock woolly adelgid

he

eastern hemlock is considered by many to be the most characteristic evergreen tree of our region. It grows in cool, shady, moist forests and on the slopes of our hills and ravines, often in extensive stands.

A mature hemlock can grow to at least 70 feet in height and live for hundreds of years. The tree's shape is conical, with slightly drooping branches growing nearly down to the ground. The needle-like leaves, unlike those of pines and spruces, grow in flat, double rows. Years ago a naturalist taught me that if you take a few needles and crush them between your fingers, you get a delicious, resiny aroma.

Ecologically speaking, the hemlock is an important tree in our forests, providing shade and shelter for wildlife in all seasons.

White-tailed deer feed on hemlock leaves. Eastern screech-owls and saw-whet owls may be found roosting within the dense foliage. The shade along streams also helps keep the streams cool - important for fish favored by anglers - and hemlock stands stabilize soil and help purify water that feeds wetlands. The hemlock is also a popular ornamental tree in dooryards and gardens.

But, like the

American chestnut that I wrote about a while ago, the eastern hemlock has been devastated in the past two decades by an introduced pest, a small aphid-like insect imported from Japan known as the hemlock woolly adelgid . The adelgid feeds on the leaves at their joints, turning them brown and weakening the tree.

A mature hemlock can die from adelgid infestation within four to six years. Many forests throughout the state, particularly in the eastern half of Connecticut, have been hard hit. The adelgid is a relative newcomer to the Northwest Corner; our towns were among the last in the state to receive the pest, which now covers the entire state.

Fortunately, a biological control agent pioneered for use by our very own Connecticut Agricultural Experiment Station (CAES) has shown promising signs of being able to manage the adelgid and restore hemlock forests. The agent is also a Japanese import, a species of

Asiatic ladybeetle - fortunately, not the same one that homeowners in our area know as the bright orange pest that gathers in occasional breakout numbers on walls and ceilings. This one's much smaller, and black. It is presumably a natural predator of the adelgid in Japan, and seems to be adjusting to a similar role here.

Dr. Carole Cheah of the CAES has guided the adelgid control project in Connecticut. Close to 200,000 beetles have been released in the state so far, and initial indications are that some of the mostly heavily damaged areas are showing signs of recovery. We can only hope that the introduction of the ladybeetle in our area will head off the problem before we lose our lovely hemlocks.

Fred Baumgarten is a naturalist and writer. He can be reached at fredb58@sbcglobal.net. His blog is at thatbirdblog.blogspot.com.