DURHAM, N.H. — Scientists in the northeast are asking hikers, hunters and others to watch for telltale signs of a beetle that has killed millions of ash trees.

Colleen Teerling, a Maine Forest Service entomologist, says heavy woodpecker activity is a good sign that the emerald ash borer is present. It has destroyed trees in 22 states — including several in the northeast and New England — and two Canadian provinces since it emerged in Michigan in 2002.

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Kyle Lombard, New Hampshire’s forest health manager, says with the leaves off the trees in autumn, people can easily spot the cream-colored bark revealed when woodpeckers strip off chunks of outer bark.

People who see woodpecker activity should contact their state forest health manager.

Ash trees have deeply furrowed bark with a distinctive, diamond-shaped pattern.