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Battling a giant killer

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Science  21 Aug 2015:
Vol. 349, Issue 6250, pp. 802-805
DOI: 10.1126/science.349.6250.802

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The eastern hemlock is one of eastern North America's largest native conifers. It has been called the "redwood of the east" and the "queen of the conifers." A healthy tree resembles an evergreen waterfall; overlapping layers of short, downy needles cascade from the crown almost to the ground. But the iconic tree, found from Georgia to Canada, is under attack. The hemlock woolly adelgid, a tiny sap-sucking insect about the size of a pinhead, has infested more than half of the hemlock's range, killing countless trees. Barring human intervention, it ultimately kills nearly every tree it attacks. Forest managers have been fighting a fierce battle against the adelgid. Many hemlocks are still alive because they've been treated with insecticides. But that's an expensive and labor-intensive tactic, so scientists are searching for more sustainable, long-term strategies. They're rearing and releasing predatory insects that eat the adelgid, for instance, and even looking for rare genes that might help them breed resistant trees. The question is whether such efforts will mature in time to prevent the adelgid from essentially removing one of the defining species from the eastern forest. Eastern hemlocks, warns forester Jesse Webster of Great Smoky Mountains National Park, "are in intensive care."

  • * in Highlands, North Carolina; photography by Katherine Taylor. Gabriel Popkin is a freelance writer in Mount Rainier, Maryland.

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