It was just a matter of time. After predicting that the emerald ash borer would eventually infest trees in the village, Riverside’s village forester announced in January that the wait is over.

In late December, said Michael Collins, the pest was found inside an ash tree located in the triangle at the intersection of Repton and Southcote roads in the northwest corner of the village. It is the first, and so far only, tree known to have been infested with the emerald ash borer.

The 10-inch diameter ash tree was located in an area where the Illinois Department of Agriculture had placed a trap last spring. An adult emerald ash borer was found in the trap last fall, but it was not known at that time if it signaled an infestation in Riverside. Two other adult emerald ash borers were found in traps at the nearby intersection of Southcote and Uvedale and in Indian Gardens in the far south end of the village.

In 2010, an emerald ash borer was found in a trap near Blackhawk and Riverside roads.

When the tree in the Southcote/Repton triangle was removed, Collins said he discovered that the insect had probably infested the tree two years earlier, judging from the damage inside.

“It matches when we first found it in a trap,” said Collins. “It just took time for us to see the symptoms in trees.”

There are six more ash trees in the Repton/Southcote triangle, ranging in diameter from 6 to 20 inches and between 25 and 60 years old. All of them will be taken down in 2012, said Collins, in addition to three ash trees, including a 23-inch diameter specimen, in a triangle just across the street.

In December a total of 33 ash trees were cut down throughout the village. All of them had exhibited “structural defects,” according to Collins. Only the one was infested, however.

Earlier in 2011, crews took down another 30 ash trees as part of a federal reforestation grant the village received. Riverside has around 1,100 ash trees on public land. An unknown number remain on private land and on forest preserve property bordering the village.

During the 1980s and 1990s, the ash tree became a favorite of urban foresters, said Collins. Prior to the discovery of the ash borer, the ash was seen as a fast-growing, hardy specimen that was resistant to pollution and fared well in harsh conditions on urban parkways.

“For a long time it was considered a great tool for urban foresters,” Collins said.

The ash borer was first discovered in the United States in southeastern Michigan in 2002 and found its way to Illinois in 2006, according to the website, a clearing house of information about the pest created jointly by the U.S. Forest Service and administered by Michigan State University.

Since 2002, the pest has spread throughout the Midwest and into the Mid-Atlantic states and into Canada, destroying tens of millions of trees.

On the heels of the ash borer discover in December, Riverside’s village board on Jan. 17 approved a new policy related to the removal of ash trees in the village with an eye toward reforestation over prevention.

Letters will begin going out to residents whose properties are adjacent to ash trees on public parkways later this month. The letters will lay out three options.

Homeowners can simply wait until the ash tree becomes infested, at which time the village will take down the tree at its own expense. Or, a homeowner could ask the village to pre-emptively take down the ash tree before it becomes infested. That will allow the village to schedule removals and place those areas on a list for reforestation sooner. Again, there would be no cost to the homeowner for removal of that tree.

Finally, the homeowner could choose, at his own expense, to treat the ash tree with a chemical insecticide to prolong the life of the tree. If the tree becomes infested at any point, however, the village will remove the tree.

“What we’re trying to do is avoid letting these trees get to the point where they’re half dead,” said Collins.

Collins said the village will not treat ash trees on its own. Collins said he’d rather spend money on removing and replanting trees than on long-term annual prevention.

“A lot of my approach on this is letting trees with known insect pressure go,” Collins said. “It’s a great opportunity to take that 10 percent and turn it into a more species-diverse population.”

The cost for injecting a tree with insecticides is between $4 and $8 per inch of diameter, said Collins. If you’re injecting a 10-inch tree annually, it will run you at least $40 a year. In six years, you will have spent $240 to save the tree.

“That’s pretty much the price of a new tree,” said Collins. “After the 10th year you could have paid for the removal and replanting of the tree. I just think in terms of the long-term commitment, it’s not realistic.”

Once a tree is found to be infested with the emerald ash borer – on private or public property – it must be removed. In 2009, the village passed a law requiring private property owners to remove infested trees within 30 days of being notified by the village. If the property owner fails to do so, the village can, by law, have it removed and bill the homeowner.

So homeowners who have ash trees on their properties are faced with a dilemma – pay to treat the trees annually or bear the cost of removal sooner or later.

“It’s a tough decision,” said Collins, “because everyone is emotionally invested in their trees. In terms of private property, it’s going to be a tremendous burden for our residents.”