Scientists searching for way to stop ash borer's spread

Chris Young

Scientists are rushing to find a way to slow the spread of the emerald ash borer as it devastates ash trees in North America.

Native trees are at a disadvantage because they have not developed an association with the beetle from Asia over time.

“Asian ashes probably have some genetic resistance since they evolved with the beetle,” said Phil Nixon, extension entomologist with the University of Illinois.

The emerald ash borer also lacks natural enemies on this continent. The U.S. Department of Agriculture has brought over three parasitic insects that help control the borer at home, Nixon said. They are being tested in Michigan.

“But there is always a risk when you are trying to close Pandora’s box by opening it again,” he said of bringing additional, non-native insects into the country in hopes of controlling an invasive pest.

Most biological control agents fail, although researchers are hopeful this time because the parasitic insects do a good job of controlling the emerald ash borer back home.

And biological controls are limited because they thrive by co-existing with other organisms, not eradicating them. If a hawk eliminates all of its potential prey, it will starve. The goal is equilibrium, not eradication.

Efforts to restore the American chestnut hinge on taking traits from Chinese chestnut trees, which are resistant to chestnut blight and crossing and back-crossing several generations until the only Chinese trait that remains in the native tree is the resistance to blight.

“But that disease came through 70 to 80 years ago, and they are still working on it,” said Nixon.

More effort is being spent on creating genetically modified trees that are resistant to the ash borer in a relative short period of time, Nixon said. Scientists are trying to identify the genes that help provide resistance.

“They’re looking in that direction,” he said.

Officials are taking drastic measures, too.

“They have been saving ash seeds already,” he said. “Theoretically, if you let all the ash trees die (and the borers die from starvation), a decade later you can come back and replant.”

That’s where treating trees with pesticide makes things complicated.

The fear is that any living ash trees will harbor enough emerald ash borers to start over again.

“By protecting their ash trees, they are protecting the ash borer, too,” Nixon said.

Chris Young can be reached at (217) 788-1528.