Alien Invaders of Our Forests

Watch out for the Big Three of Forest Pests in New Hampshire

Hemlock woolly adelgid.
Photo by Steve Roberge

If you’ve ever been horribly sick, you know the power of a tiny bug to cause harm and disruption.

Our forests aren’t immune from the power of tiny bugs. Even as sprawling and resilient as forests are, they face potentially enormous threats from small pests so small you could fit a bunch on a penny.

Three pests in particular deserve their mugs on a most-wanted poster for threatening our forests: emerald ash borer, hemlock woolly adelgid and Asian long-horned beetle. Those are the big three that foresters like Steve Roberge worry about.

“All three of these pests have the potential to change the way our forests look,” says Roberge, who lives at the N.H. Division of Forests and Lands’ Shieling Forest in Peterborough and is the UNH Cooperative Extension forester for Cheshire County.

All three have unique differences and affect trees and forests in different ways, according to Roberge and other foresters.

But they all share at least one commonality: They’re not native to North America. As such, our trees and forests lack the protective defenses against their potential harm. And as non-natives – with nature providing few elements to keep their numbers in check – they can spread like crazy if we’re not careful.

That’s why Roberge and others concerned about forest health want to spread the word about these big three. “The key to all three of these pests is early detection and an informed public,” Roberge says. “We should never let our guard down with all three of these. We want to have an informed public to make sure they know what these pests look like and what the signs of their damage look like.”

Early detection, Roberge says, can help prevent them from spreading and becoming a costly endeavor to eradicate.

So here’s a look at the big three:

Emerald Ash Borer

This little beetle from Asia was found in 2002 to be causing widespread mortality to ash trees in Michigan and Ontario. Larvae feeding on the tissue between the bark and the sapwood disrupt the flow of nutrients and water, eventually killing branches and the entire tree.

Since 2002, the emerald ash borer has killed tens of millions of ash trees as it has spread to 18 states, most recently in western Massachusetts in August. While not detected in New Hampshire yet, it has potential to seriously damage ash trees here, which are important part of our hardwood forests and provide an excellent source of heat for our homes.

Asian Long-Horned Beetle

A bit bigger than emerald ash borer, the Asian long-horned beetle is up to 1½ inches long, with very long black and white banded antennae. It is believed to have arrived in the U.S. in the 1980s via wood packing material coming into a port in Brooklyn. Since then, it has spread to many states and provinces and has been found in Worcester and Boston, Mass. In Worcester, tens of thousands of trees have been removed because of an infestation there.

Maples are a particularly favored host of the Asian long-horned beetle. If a serious infestation takes hold in New Hampshire, it could devastate maples, which are important to our maple sugar industry and are a critical part of our hardwood mix.

Hemlock Woolly Adelgid

This is a small aphid-like insect that feeds on hemlock and, if left untreated, can kill a hemlock within four to ten years, often by weakening the tree’s defenses from other pests. Introduced in Virginia in the 1950s, it has since spread from Maine to Georgia. And it’s already here. In our region, hemlock woolly adelgid has been found in Peterborough, Greenfield and Jaffrey.

The insect can be recognized by a dry, white woolly substance on the young twigs of hemlock. This woolly stuff is a defensive covering over the insect’s body.

While hemlock is often considered a species of low commercial value in New Hampshire, there’s no denying its importance to the ecosystem. Because of its habitat preferences and growth characteristics, the hemlock is like a forest’s ultimate shade and cover creator. It provides cover and habitat for white-tailed deer, wild turkey, fisher, porcupine, blackburnian warbler and many other species. It keeps forest streams cool for Eastern brook trout.

Losing hemlocks – or suffering impaired populations – could wreak havoc on the above species that are now fairly common. No other tree provides the same ecosystem service as the hemlock.

You Can Help

While it’s possible that these species will ultimately invade our forests, Roberge and other forest health advocates say we should not give up and should not let down our guard.

Owners of forestland can take many steps to protect to prevent, slow or limit the spread of nasty invasives. A key part in that is early detection through an informed public, not just foresters, loggers and land managers, but folks like you who enjoy the forest for all it provides.

Another step is to make sure you don’t inadvertently move forest pests via firewood. Pests can travel in firewood at various life stages, so don’t help spread infestations by buying untreated firewood from out-of-state or long distances, say 50 miles or more.

For more information about invasive forest pests, visit dontmovefirewood.org, or http://extension.unh.edu/fwt/cpestssub.cfm?sear=3. Also, check out this video: Trees, Pests and People.

Steve Roberge will give a talk on the “The Emerging Forest Pests in New Hampshire,” Thursday, December 6, 7 p.m., at the Keene State College Science Center. The talk is sponsored by the Harris Center for Conservation Education, the University of New Hampshire Cooperative Extension, and the Keene State College School of Sciences.

Eric Aldrich writes from his home in Hancock.