By Rowena Lindsay
Hemlock woolly adelgids aren’t native to North America, but droves of them have settled into American forests where they threaten entire ecosystems.
A tiny bug, no bigger than a grain of pepper, is wreaking big-time havoc in US forests, and forest managers are scrambling to keep up.
Hemlock woolly adelgids aren’t native to North America, but droves of them have taken up residence in hemlock forests, from New England to the West Coast, thanks to increased trade and travel. Nestled under the needles of hemlock trees, the invasive insects cut off nutrients to the tree and can eventually take down trees that have stood for 300 years.
If left unchecked, the hemlock woolly adelgid and other pests are projected to put 63 percent of the nation’s forests at risk by 2027, according to a study published this year in the journal Ecological Applications. The tiny invaders could put several species of hemlock at risk for extinction, threatening the biodiversity and stability of ecosystems across the country and cutting a carbon sink for mitigating greenhouse gas emissions.
Globalization has opened the door for hundreds of invasive pests, from the Asian longhorned beetle to the emerald ash borer. And climate change, it seems, will make it even more difficult to evict them.
Invasive insects cause at least $77 billion in damage every year, according to a study released Tuesday that says this figure is “grossly underestimated” because it covers only a fraction of the globe.
Climate change is on track to boost the area affected by nearly 20 percent before mid-century, the authors reported in the journal Nature Communications.
Canvassing more than 700 recent scientific studies, researchers looked at the impact of non-native species on goods and services, healthcare and agricultural output.
Most of these studies applied to North America and Europe, which means the devastation wrought by crop-chomping and disease-carrying bugs from afar has not been adequately measured, the authors said.
The most destructive of the insects canvassed was the Formosan subterranean termite, which lives in huge colonies and feasts on wooden structures and living trees.
An insect responsible for the loss of much of the eastern United States Appalachian region’s hemlock trees has found its way into Michigan. The hemlock woolly adelgid poses a threat to the state’s valuable hemlock stands. A call to action by citizens may be the most realistic path to further detection and control.
Justin Whitehill is hopeful that “we will eventually be able to produce EAB-resistant ash trees by borrowing from other ash trees that have natural resistance. Applying modern genomic technologies to conventional tree-breeding methods has the potential to preserve not only a single species, but a whole genus that is being impacted worldwide.”
Paul Merten has spent nearly a decade chasing down a killer in the Southern Appalachians, armed with no more than a pocket knife and measuring tape.But recently the entomologist with the U.S. Forest Service in Asheville, N.C., has been homing in on the tiny, yet lethal pest with what he hopes is a secret weapon — parasitoids, also known as wasps.Merten and Haywood County Community College forestry student Caroline McGough were deep in the woods on the Appalachian Trail slicing across the North Carolina-Tennessee border last week, unleashing parasitoids in a science fiction-like attack on the emerald ash borer.
Researchers here are hatching a plan to stop the woolly adelgid. A 1-acre plot of forest is the site of a budding insectary, a farm in the trees of the predator beetle Laricobius nigrinus that has been shown in some cases to kill the adelgid.