Mount Vernon Emerald Ash Borer Treatment 'Working'

Published: Mar. 15, 2016 at 12:48 PM CDT
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It’s working. That’s what Mount Vernon Horticulturalist Mike Wehde says about an ash tree treatment aimed at stopping the spread of the emerald ash borer.

For two years, Mount Vernon has been injecting city ash trees with a chemical called TREE-age that kills beetle larva. To date, 211 trees have received the treatment. Wehde said none have shown signs of infection.

"It's probably the best system right now," he said. "Pretty much a 97% kill ratio of the larva."

Iowa’s first confirmed case of the beetle was in 2010. Since then, it has spread to 31 counties, including Linn, mostly in the eastern half of the state. More than a third of the new locations have come in the last year, state agriculture officials said.

In February, the EAB was discovered in Johnson County by facilities workers at the University of Iowa. The workers noticed trees showing symptoms of an ash borer infestation.

Common evidence includes thinning or dying branches in the upper canopy S-shaped feeding galleries on decayed bark, and D-shaped exit holes.

The borer is metallic green in color and about a half-inch long. Its immature stage feeds on the inner bark of ash trees preventing them from distributing nutrients and eventually leading to their death.

Wehde says the injections are costly. Mount Vernon estimates it'll pay $30,000 every three years for the chemicals.

Many other communities are taking what could be a cheaper route, cutting down ash trees and planting different species to slow the beetle's spread.

Cedar Rapids has been removing trees since 2010. The University of Iowa has said they'll be doing the same because of the advanced age and poor health of many of their ash trees.

Wehde says tree removal can cost one to two grand. Considering Mount Vernon has hundreds of ash trees, he thinks the injections might be cheaper in the long run for the town.

"Plus, you still got the tree," said Wehde. "It's still standing, still growing, still taking up water, giving off oxygen and all the things that we plant trees for."