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City of Duluth provides status update on Emerald Ash Borer

[Duluth, MN] The City of Duluth has been actively managing ash trees since 2016 to slow the spread of the Emerald Ash Borer (EAB), an invasive beetle that attacks ash trees. EAB bore into ash trees and damage their ability to take up water and nutrients. The process will kill the tree in two to seven years depending on the tree’s age, size, and initial vigor. Dying ash trees need to be removed because they become brittle and are at much greater risk of storm damage, which could result in falling branches and limbs.

EAB overwinter as larvae, and those larvae survive the winter under the bark of their host ash tree. The bark serves as insulation and warms in the sun, which provides protection from the cold. There is some indication that not all EAB larvae are able to survive sustained air temperatures below -20°F. How larvae adapt and respond to the local climate does influence the future EAB population. The extensive population of EAB in Duluth would require a very harsh winter for any noticeable impact. Unfortunately, for Duluth’s ash, the recent cold snaps have not reached low enough temperatures for long enough periods to effectively reduce the EAB population.

To help remove ash trees, the City of Duluth secured two grants in 2022 from the Minnesota Department of Natural Resources to support the removal and replacement of dying ash trees.

• $99,081 through the Protect Community Forests grant program
• $150,000 through the Preparing for Emerald Ash Borer grant program

With these 2022 grants, the City has secured a total of $810,562 in state grants. With this state assistance, the City has, thus far, removed and replaced 1,800 dead and dying ash trees out of an initial population of 3,200. Going forward, the City aims to remove and replace 400-600 more trees per year in hopes of completing removal and replanting in 2026. Replanting efforts prioritize establishment of a more sustainable urban forest that will be less vulnerable to new invasive species that may arrive in Duluth in the future. The City has also been collaborating with the Minnesota Land Trust to plant replacement trees in ash woodlands within the estuary landscape.

For more information about the EAB and the City’s response, please visit https://duluthmn.gov/parks/natural-resources/invasive-species/eab/

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