Village foresters in both Riverside and Brookfield have set traps to check for the presence of the emerald ash borer in their ash tree populations, hoping to head off an infestation that is ravaging trees across the Midwest.

The emerald ash borer, a one half-inch long, bright green beetle, was first detected in Michigan about five years ago, and since then it has spread to Indiana, Ohio and, as of this summer, Illinois. According to the Illinois Department of Agriculture, over 20 million ash trees in the region are dead or dying due to the pest.

In Illinois, the emerald ash borer was first discovered in June in Kane County. In July approximately 30 trees in Wilmette and Evanston were also found to be infested by the beetle.

According to the Morton Arboretum Web site, the emerald ash borer infests trees by laying eggs on their outer bark. Larvae then feed on the inner bark, boring through the tree to create large, S-shaped tunnels throughout the trunk. The tree will then wither and die within about three years.

In order to detect infestation in Brookfield, four “trap trees” have been set up throughout the village. Village Forester Scott DeRoss explained that these traps involve stripping an ash tree of its bark in order to attract the beetle. In the fall, after the emerald ash borer’s flying season has ended, the trees will be cut down and sent to the Morton Arboretum, where each branch will be checked for signs of the pest.

This is the second year Brookfield is monitoring for the emerald ash borer, DeRoss said. Last year, two trap trees were set, both of which later came back negative.

“So far, thank God, we haven’t had them,” he said, adding that of Brookfield’s 9,000 trees, about 1,600 of them are ash trees.

In Riverside, Forester Mike Collins said six trap trees have been set up. Three of those will be harvested this fall, with the rest collected in the fall of 2007. This is the first year Riverside is monitoring for the beetle.

Collins said the village is especially concerned about the possibility of an infestation because the ash tree is one of the few plant species specifically identified in the original Olmsted Plan laid out the Riverside in the late 19th century. Collins estimated that there are approximately 1,100 ash trees just on the village’s public land.

No traps have been set in North Riverside. Public Works Director Tim Kutt said the village was awaiting further instruction from state authorities, who he said are still in the process of determining how to respond to the new infestations.

Indeed, a decision is still to be made as to what to do with infested trees. According to Jeff Squibb, a spokesperson with the Illinois Department of Agriculture, a quarantine area has been set up around the infested trees in Kane County, banning the transportation of firewood out of the area, but there are no set plans on how to control the spread of the infestation. He noted that in other states’ officials had decided to cut down all ash trees within a half-mile radius of an infected tree, but said that wouldn’t necessarily be the case in Illinois.

“Yes, there will have to be trees removed,” he said, “but there is no hard and fast rule. Right now, we have staff taking a look at the options available, finding out what’s worked and what hasn’t worked.”

Squibb said a decision would be made by the fall, with no trees being removed before September.

Whatever the final decision, a large-scale infestation in the area could be very costly. Collins said it would cost roughly $700,000 to cut down every ash tree in Riverside, and an additional $300,000 to replant them.

“An infestation here would be a tremendous financial burden,” he said.

Because of the seriousness of the threat, residents in all villages are urged to be on the lookout for potential signs of the emerald ash borer. Collins said the most visible signs of an infected tree would be a dying back of the crown, as well as new branches sprouting from the tree’s base. More information can also be found at the Morton Arboretum and Illinois Department of Agriculture Web sites, as well as