Scientists hope to buy time for threatened ash trees

When Mark Whitmore goes for a walk down his street in Ithaca, New York, he sees nothing but trouble.

“You see in the distance there’s another green ash behind somebody’s backyard. There’s about a dozen houses near that and that tree could hit any one of them when it falls.”

Whitmore is a forest entomologist at Cornell University, and he’s been keeping a wary eye the emerald ash borer. Whitmore says when the iridescent green beetle gets here homeowners and the city will have to deal with a dangerous and expensive problem.

“Here we have all these power lines. It’s never cheap working on a tree in an urban situation”

His grim outlook stems from what’s been happening all over the Midwest.  With no natural predators to control the population, the pest has multiplied rapidly, killing tens of millions of trees in Michigan alone.

Now, with a big assist from campers who move infested firewood around, the emerald ash borer has spread to 15 states and Canada. Everywhere, says Whitmore, it’s leaving dead ash trees behind.

“It’s looking to be pretty much complete mortality, and that’s the shocker of the thing.”

It’s the insect larvae that do the damage. Dr. Julie Gould of the U.S. Department of Agriculture says larvae can kill a tree in just 2-3 years, by boring serpentine tunnels called galleries under the bark.

“If you have a thousand of these galleries all cutting off the flow of nutrients, the tree simply cannot survive that large of an onslaught and it will die.”

None of North America’s 15 species of ash have shown any resistance to the borer, so the potential economic losses are large. The valuable hardwood is used to make furniture and flooring, shipping pallets, tool handles, and even baseball bats.

Scientists have been working to lessen the impact, trying to buy time for cities and landowners to adjust. So far, the best hope lies with introducing another non-native species into American forests.

After bushwhacking through the woods in the Hudson Valley near West Point, Gould and a colleague are releasing tiny, non-stinging wasps native to China (the natural predator of the ash borer). It’s part of a 12-state study. Researchers want to see if the wasps can slow down the ash borer by attacking those voracious larvae.

“We’re hoping to re-establish that relationship here in the United States so that something is killing the emerald ash borer and reducing its population numbers,” said Gould.

The USDA started the project four years ago. Cornell’s Mark Whitmore says it might work, but probably not before the emerald ash borer kills nearly all the ash trees we have.

“So we need to start considering how we’re going to preserve the genetics so we can perhaps bring these back in the future.”

The federal government has imposed a quarantine on areas where the ash borer has been found, limiting movement of untreated ash. But it is also pursuing that Plan B: Collecting seeds to study and plant at a time when ash may be able to survive the invader.