A Biological Approach to Tree-Killing Ash Borers

Jun 10, 2021

The emerald ash borer has killed hundreds of millions of trees nationwide, and the federal government imposed a quarantine to try and stop its spread.  Now, foresters are taking a different approach – working with nature to battle the bug.

Charlottesville forester Mike Ronayne hopes a new USDA program will stop the emerald ash borer from killing trees at the Ragged Mountain preserve.
Credit RadioIQ

It’s been nearly twenty years since the emerald ash borer arrived in America from Asia and began killing trees here.  Scientists said the bugs were spreading in firewood, and the USDA urged us not to move it from one place to the next.  There were signs and public service announcements on radio and TV.

“You move fire wood, you spread the beetle to our forests and our neighborhoods," says the ad. "Help stop the beetle!  Promise you won’t move fire wood.  I promise not to move firewood!”   

But the bugs spread anyway – infesting trees in 35 states and the District of Columbia.  In Charlottesville, urban forester Mike Ronayne says ash borer eggs kill trees by blocking needed nutrition.

“When the eggs hatch, the larvae burrow underneath the bark, and they disrupt how the tree moves food around.

Now, he says, scientists have come up with a new way to attack the ash borers – introducing a tiny wasp that feeds on the bug’s eggs.

The emerald ash borer kills trees by laying its eggs under the bark, disrupting the flow of nutrients.
Credit USDA

“People have been doing this in other parts of the country for some time now," he explains. "It’s been documented as very safe. They do not sting, and they’re very small wasps. I don’t think people are going to notice these.”    

Charlottesville is one of several communities around the state working with the USDA to introduce and track wasps over the next five years – hoping to demonstrate that this biological approach to pest control will prove more effective than limits on the transportation of firewood.