Columnist Geri Nikolai on invasive beetles.

If we all keep our eyes open, we can protect Illinois woodlands and streets from losing trees to the emerald ash borer, says an agriculture specialist who works for University of Illinois Extension.


The emerald ash borer is a bright green beetle that kills trees by burrowing into bark and harming the trees' ability to bring water from the roots to the upper branches. The nasty little bug has had a field day in recent years, killing 12 million to 20 million ash trees in Michigan, Indiana and Ohio.


Illinois officials are determined to protect our ashes, and Andy Larson of UI Extension says it can be done, even though the borer has been confirmed in Cook and Kane counties.


"The emerald ash borer does not travel long distances by itself. It spreads by firewood or live tree transfers," Larson said. "We are doing our best to keep from moving that kind of ash product."


The state Department of Agriculture is treating the Cook and Kane county infestations by applying insecticides, destroying some trees and quarantining firewood. Each infestation has affected fewer than 20 trees in a small area, so treatment is possible, Larson said.


Ash trees make up 10 percent to 15 percent of the tree stands in local forest preserves, said Winnebago County Forest Preserve arborist Dave Reithmeier, who estimates that 10 percent or more of all trees in the county are ash.


"They are popular as landscape trees, especially the black or purple ash," he said.


Here is what experts say we should know about the emerald ash borer:


- Adults are metallic green and a half-inch long.


- They leave D-shaped exit holes in bark when they emerge in spring.


- Other signs are thinning and yellowing leaves.


- They attack only ash trees.


- Woodpeckers like borer larvae; if you see lots of woodpeckers on an ash, it may be a sign of infestation.


Other bugs can be mistaken for this one, so don't panic if you think you spot one. Instead, call the UI Extension's master gardener office at (815) 986-4357 from 9 a.m. to noon and 1 to 4 p.m. Mondays through Fridays. They'll help you determine if you've got the real thing and know whom to contact to contain and kill it.


A good Web site for more information on this is www.emeraldashborer.info.


Geri Nikolai writes about home and garden for the Rockford Register Star. Contact her at (815) 987-1337 or gnikolai@rrstar.com.