A potential ally for one of North America’s most embattled trees has passed its first big test. A tiny predatory beetle that researchers have been rearing and releasing into forests appears to be doing damage to an aphidlike pest that poses a deadly threat to ecologically important eastern hemlock trees, a 5-year study has found.
The result marks a rare success for forest scientists aiming to use introduced insects to battle pests, a strategy called biocontrol. Researchers caution that hemlocks are far from safe, however, because it is unlikely the beetle alone can defeat the pest. But the news “gives some cause for encouragement,” says Aaron Ellison, an ecologist at the Harvard Forest, who is not involved in the work.
Sometimes called the redwood of the east, eastern hemlock (Tsuga canadensis) is an evergreen giant inhabiting forests in eastern North America from Alabama to southern Canada. Its dense shade cools mountain streams, and its leaves and branches host hundreds of insects and other arthropods. It can form almost pure stands in the forests of the northern United States and Canada, making it a foundational species.
