Ash borer becomes an even bigger pest in Oak Creek

More ash trees dying this year than ever before

July 1, 2014

Oak Creek — According to one city official, more ash trees are dying this year as a result of emerald ash borer than ever before.

"We are pretty much inundated this year," said Rebecca Lane, Oak Creek's city forester.

EAB, an invasive green beetle that is native to Asia and Eastern Russia, was first detected in Oak Creek in 2009, but is presumed to be in its 10th year of infestation in the city.

Lane suspects this year's severity is a result of the ash borer's ability to establish itself in the city's tree population over the course of the decade. Ash borers often go undetected for a time after they arrive.

Fighting back

Residents who identify an ash tree that shows signs of the ash borer's presence are urged to report it to the city so it can be evaluated.

Every ash tree that is removed is replaced with another tree species, Lane said, but the city also has a treatment program in place. Ash trees can suffer the effects of infestation quickly, but their deaths are preventable if treated early enough.

Through a partnership with Legacy Tree Project, Oak Creek had been given five years worth of soil injection treatment with an insecticide called Safari, whose active ingredient is also used in some flea-and-tick-control products for pets.

This is the last year of the LTP program, but Lane expects the city to continue treating ash trees.

Oak Creek has 750 street ash trees, 125 of which have received treatment from LTP. The city has also already removed 1,000 rural road ash trees.

Wasps in the woods

Lane said woodland ash trees are not managed because "it would be close to impossible," but the state is at least trying to address that problem.

Last year, state's Department of Natural Resources released stingless wasps into Wisconsin woodlands as part of an effort to introduce a species that could help fight the ash borer infestation.

The female wasps can detect where ash borer larvae are located under the bark of a tree. The wasps bore into the beetle larvae and lay their eggs there. As the wasp eggs develop, they feed on the ash borer larvae, eventually killing them.

Minnesota natural resource officials say the approach has shown signs of success, but data is not available yet of its impact in Wisconsin.

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