Learn more about survivor trees (interview starts about a minute in)

Researchers with the U.S. Forest Service are looking for ash trees that survived the attack of the emerald ash borer.

The invasive insect has been spreading across the Midwest and beyond since 2002 - killing millions of ash trees in its wake.

Here's an animation showing the spread of the emerald ash borer from 2002 to 2014:

The Northern Research Station has launched a new online reporting tool. They want people in 10 counties in southeast Michigan and 7 counties in northwest Ohio to report the location of ash trees that have survived the infestation.

Jennifer Koch is a research biologist with the U.S. Forest Service. She explains where to look for the trees and why:

"What we're most interested in are trees that are in natural wooded areas, we really want people to go look outside of their homes and their streets and into the woods and the forests."

Not all ash trees qualify for study

She says trees that are planted in your yard and street trees are most likely from local nurseries and are horticultural cultivars. She says these trees have limited genetic diversity and are probably already in the researchers' collection of trees to be tested. Also, ash trees in yards and cities that survived the borer were often treated with insecticides.

Ash trees in forests, though, are more likely to have survived on their own.

"What we're really focusing in on is trees that have maintained a healthy crown, so very few branches with any dying leaves or anything like that, in an area where most of the other ash trees are dead, " she says.

The researchers also want you to keep an eye out for big ash trees: trees with a minimum of a 10-inch diameter at 4.5 feet high. This measurement, known as diameter at breast height or DBH, assures researchers that the tree was big enough when the ash borer infestation was at its peak. That's because the insects like to attack bigger trees.

For more tips on how to identify ash trees, click here.

Breeding for resistance

Koch says researchers will use the information from the reporting tool to try to understand what mechanisms allows these survivor trees to flourish while their counterparts succumbed to the invasive insects.

"We want to determine if that is a genetically heritable trait, because if it is a genetic trait, we can then breed for it. Our ultimate goal is to be able to breed for resistance," Koch says. "And to do that, we have to be able to identify trees that have this rare combination of genes that may allow them to tolerate emerald ash borers longer than their counterparts."

Koch adds that resistance to the ash borer is critical to maintaining ash in Midwestern forests.

If you want to help find survivor trees, first: take a walk in the woods and try to spot a healthy ash tree. And if you think you’ve found one, you can enter information about the tree using the survivor tree reporting tool.