City's Fight Against Emerald Ash Borer Continues

Oak Creek is continuing its efforts to minimize the emerald ash borer's impact.

The Oak Creek Common Council on Tuesday approved rehiring M&M Tree Service, with a low bid of $15,198.25, to treat about 575 trees in spring and fall.

The treatments are in response to the invasive beetle, first discovered in Oak Creek in November of 2009 and believed to be in the city for the previous eight years.

The emerald ash borer is a highly-invasive, destructive insect that feeds on the sap of ash trees, which are common in Oak Creek and throughout Wisconsin. Once an ash tree is infested with ash borer larva, it can die within a year.

Treatments to minimize their effect have taken place in Oak Creek for the past two-and-a-half years.

Arborist Paul Sutor of M&M Tree Service said that treatment needs to be done annually to keep the trees healthy.

"Emerald ash borers are very devastating," Sutor said. "If untreated, the population builds up and when the population of the borer explodes, it just wipes out every ash tree."

The treatment consists of an insecticide mixed with water and fertilizer, which is injected into the soil near the base of the tree, Sutor said. The amount of insecticide is strictly measured based on the size of the tree. Once absorbed into the tree, the treatment is 90 percent effective at controlling the beetles.

City Forester Rebecca Lane said the biggest problem areas are the southwest and northeast corners of Oak Creek, but the infestation is now fairly widespread.

"It is assumed that it is everywhere, since we could find it in patches or individual trees throughout the city," Lane said.

The city has an estimated seven-year plan to remove and replace all ash trees in the city. However, residents living on streets lined solely with ash trees will have the choice to individually remove or treat the trees.

"Some residents would rather not have chemicals in their yard," Lane said. "That’s fine, they can choose to hang on to them longer."

Sutor said the insecticide typically causes the grass around the tree to become greener because of the fertilizer. The treatment has no negative effects on the grass or soil.

Dead or diseased trees must be removed under an ordinance that was changed last year, but property owners can determine the fate of trees that have not been infested. Treatment letters containing more information on the project and private removal options were expected to be distributed to residents this week.

Since 2007, the city has removed more than 1,000 ash trees. Between 50 and 100 ash trees continue to been removed each year, Lane said. She expects all of the ash trees will be removed and replaced in the next five to ten years.

The project is funded through the Forestry Capital Improvement Program, which contains funds specifically allocated for the project. Half of the project costs are reimbursed through a Wisconsin Department of Natural Resources Urban Forestry Grant.