DNR Releasing Wasps In Battle Against Emerald Ash Borer

Oak Creek is trying a new way to battle the tree-killing emerald ash borer.

The Common Council has approved a proposal for the state Department of Natural Resources to release stingless wasps, which have been deployed elsewhere in Wisconsin and Illinois, in Oak Creek.

The wasps are less than a quarter-inch long and do not sting people or animals. City Forester Rebecca Lane said people will not notice they are present.

What they will do is slow down the spread of the emerald ash borer in Oak Creek, Lane said. The wasps kill the beetle at about a 60 percent rate.

However, some Oak Creek aldermen were leery about introducing a new species to the area. The council narrowly approved the wasp release by a 3-2 vote, with Aldermen Tom Michalski and Ken Gehl in opposition.

"We already have unintended consequences with other plants and animals being introduced into areas where they weren't native," Michalski said. "I'd just hate to come across a problem 10 years down the line that we didn't foresee."

After their introduction in northern Illinois and Newburg, Wis., it's likely the wasps would eventually make their way to Oak Creek either way, Lane said in a memo to council members. Allowing the DNR to release them now might save ash trees, she said.

Alderman Dan Bukiewicz said with the wasps probably coming to the area anyway, it made sense to do something now to try slowing down the EAB.

The release of the wasps comes at no cost to the city. The insects are provided by the U.S. Department of Agriculture, while DNR staff do the field work. It may save Oak Creek money in the long run by reducing the number of trees that need to be removed or treated, according to a report to council members.

The council delayed voting in January so it could get more information from the Oak Creek Health Department, which reported to aldermen earlier this month that the wasps do not have any known negative impacts on humans.

The initial release will likely be on the Milwaukee County-owned Oak Creek Parkway, Lane said.

The emerald ash borer was first discovered in Oak Creek in November of 2009. The beetle 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.

The city has an estimated seven-year plan to remove and replace all ash trees in the city. Treatments to minimize the beetle's impact have taken place for the past three-and-a-half years.

The DNR first announced plans to release wasps to battle the EAB in May 2011.