Invasive Species

Sometime in early 2002, a shipment was made into Michigan from Asia. The crate contained ash wood to help stabilize it. And unbeknownst to anyone at the time, the ash wood was carrying some very troublesome insects.

The Emerald Ash Borer has now invaded 22 states and Canada. It has already destroyed around 200 million ash trees, and many more are expected to be damaged and killed. The insects have invaded almost all of Indiana, though they have yet to be detected in Evansville.

But that, says TruGreen commercial manager Anthony Moffat of Evansville, is just a matter of time. And once the insect arrives, it will spread quickly.

“They found it last year in Perry County, and there is a quarantine in Dubois County,” says Moffat. “It looks like, for Vanderburgh and Warrick counties, it will be in the next 18 months. But the way this insect moves, they can’t say for sure. It could be next week, it could be next year.”

Places like Indianapolis, which already has seen the Emerald Ash Borer invasion, have lost thousands of trees. Ash trees account for about seven percent of the trees in Evansville.

“We’ve already taken some ash trees out Downtown in preparation for the pest,” says Evansville city arborist Shawn Dickerson. “We do plan to apply insecticides to some trees that are historically significant or ones that we want to try to save. But we’re waiting for it to get a little bit closer before we start doing that.”

The insects themselves are relatively small, at about a third of an inch long. Adults are a dark, metallic green color and feed on the ash canopy. The larval stage of the insect is what does the most damage, boring into the tree trunk and preventing the tree from absorbing nutrients.

“The pest will kill ash trees very similar to the way that the chestnut blight killed trees long ago,” says Dickerson. “Once the Emerald Ash Borers get into an area, they will kill every single ash tree in that area, except for the individual trees that are treated.”

While the Emerald Ash Borer adults can fly up to a half-mile on their own, they also are commonly transported by humans moving firewood or nursery stock. Dickerson says so far, there is no sign the insects have entered Evansville.

Trees can be treated to protect them from the insect. The life cycle of the insects is 10 to 12 years, meaning ash trees will need multiple treatments.

Dickerson says home and business owners with ash trees will have to consider the cost of treating the trees versus the cost of removing them. Dickerson and Purdue Extension Horticultural Educator Larry Caplan both offer free tree inspections.

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