City of Edina reminds residents to treat their ash trees

Residents or businesses with Ash trees on their properties are being advised to make sure they are treated against emerald ash borer in the next couple months if they haven’t already, Edina’s forester recommends.

“Now is the best time to treat your ash trees, from when they leaf out to July,” City Forester Luther Overholt said.

Emerald ash borer, an insect that has killed millions of ash trees across the eastern United States, was found in Edina in April 2018. It is expected to wipe out all untreated ash trees in the Twin Cities. While the extremely cold temperatures this winter killed some of the larvae, the infestation is expected to continue to spread.

As of 2018, Edina had an estimated 50,000 ash trees, most of them located on private property.

Chemical treatments can help protect healthy ash trees or those minimally affected by the pest. Treatment applications must be done every two to three years. Overholt recommends that homeowners have an arborist or tree care professional inject their ash trees with the treatment in spring.

“The best time to treat your tree is when it’s starting to grow,” Overholt said. “When they inject the chemical during the growing season, it’s easier for the chemical to get sucked up into the tree.”

Treatments spread on the ground aren’t effective for trees larger than 10 inches in diameter and also contaminate the surrounding soil and potentially groundwater with the chemical, Overholt said.

People who choose not to treat their ash trees should remove them before they become infected so they don’t contribute to the spread or pose a hazard when they die and fall.

The city of Edina is treating prominent ash trees on city property, such as those near ball fields or along boulevards.

Anyone with an ash tree on their property should contact a private arborist or tree care professional to evaluate the tree and their options.

For more information on emerald ash borer, including how to identify ash trees and signs of the pest, visit Overholt can be reached at or 952-826-0308.

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