Emerald Ash Borer


In March 2021, the first case of Emerald Ash Borer (EAB) was confirmed in Blue Earth County. The small, invasive insect infects ash trees and spreads quickly, typically killing a majority of ash trees in its path. Many Minnesota communities have seen the devastating effect of the EAB as it spreads. 


Identifying Emerald Ash Borer & Ash Trees

The first step is to inventory trees and determine whether or not ash trees are on the property. While difficult to recognize in early stages, there are telltale signs that EAB has infected a tree. It’s easiest to spot signs of EAB in the fall, winter and spring, when leaf coverage is minimal. Look for bark splitting, canopy thinning and small D-shaped exit holes. Also note increased woodpecker activity around trees – woodpeckers feed on EAB and often locate a colony before the experts can.

Typical Emerald Ash Borers are a bright, metallic, emerald green color overall, with the elytra usually appearing somewhat duller and slightly darker green. The overall greenish coloration may also have variable amounts of brassy, coppery or reddish reflections, especially on the pronotum and ventral surfaces. 


Emerald Ash Borer & Ash Tree Identification Guidelines

EAB size comparison
Emerald Ash Borer
EAB tree markings



Develop a Plan

Because EAB spreads so rapidly, it’s important to develop a plan of action as soon as the invasive species has been confirmed in the area. There are basically two options for property owners with ash trees – begin a course of treatment immediately, or plan for the tree to be removed. Find an Arborist here.



A two-year insecticide treatment typically costs roughly $100-250, depending on the size of the tree. This treatment will likely be necessary for the rest of the tree’s life. Contact a private contractor for treatment options. Less expensive do-it-yourself treatments are also available, though they are considerably less effective. Use the Homeowner Guide to Insecticide prior to beginning treatment.


Removal & Transportation

Tree removal should only occur during the inactive season for EAB (October through May). This will reduce the threat of a colony relocating. Wood from removed trees should not be transported outside the Minnesota Department of Agriculture’s quarantine area, which includes Blue Earth County. Observing the quarantine is crucial to stemming the spread of EAB.



City of Lake Crystal's Plan for Trees on Public Properties

About 30 percent of trees in Lake Crystal are ash. The City of Lake Crystal has been preparing for the arrival of EAB since 2019. To minimize the impact of EAB on trees in parks, the city adopted an EAB Management Plan, which includes:

  • Removal of smaller, unhealthy or hazardous ash trees from city parks and replanting with several different species of replacement trees. This will begin in 2021.
  • An ongoing, preventative treatment cycle on ash trees in city parks – public ash trees that are larger and in good health will begin to be treated in 2022.
  • Partnering with Community Forestry Initiative team member for identification and planning