Emerald Ash Borer

Emerald ash borers (EAB) kill ash trees. EAB is one of the most significant exotic forest pests threatening Minnesota because it has the potential to cause extensive ash tree mortality according to the Minnesota Department of Natural Resources.

Characteristics of an ash tree

  • Branches and buds are directly across from each other and not staggered.
  • Leaves are compound and composed of 5 to 11 leaflets.
  • Bark on mature trees is tight with diamond-shaped ridges, young tree bark is relatively smooth.

What does an emerald ash borer look like

  • It is a slender, elongated insect about 1/3 to 1/2 inch long.
  • It is widest just behind the head, gradually tapering back to the abdomen.
  • It is a bright iridescent green to copper-green color, often with a copper colored area behind the head.
  • It’s body underneath the wings is a purplish-magenta color.

Signs of damage from the emerald ash borer

  • Trees typically are killed in two to four years.
  • When trees are first attacked by the borer, the symptoms are inconspicuous and hard to notice. By the end of the second year, thinning foliage and dieback in the crown begins to be apparent. By the third year, there is severe dieback and little foliage.
  • When the adults emerge, they create small, 1/8 inch D-shaped exit holes that are characteristic of this insect, although they can be hard to see.
  • If you were to remove the bark on the trunk of a tree showing these symptoms, you should also find the larval galleries.
  • Woodpecker attacks on ash could also indicate the presence of emerald ash borers. Vertical splits in the bark due to callous tissue forming over old galleries may also be seen.

Firewood spreads infestation

The biggest risk of spreading EAB comes from people unknowingly moving firewood or other ash products harboring larvae. There are three easy steps residents can take to keep EAB from spreading:

  1. Don’t transport firewood. Buy firewood locally from approved vendors, and burn it where you buy it.
  2. Be aware of the quarantine restrictions. If you live in a quarantined county, be aware of the restrictions on movement of products such as ash trees, wood chips, and firewood.
  3. Watch your ash trees for infestation. If you think your ash tree is infested, go to the MDA website for resources on identifying EAB, how to hire tree care professionals, and insecticide options for protecting your ash tree.

MDA emerald ash borer information for homeowners

Reporting sightings of emerald ash borer

  1. Email Arrest the Pest or leave a detailed phone message at 1-888-545-6684.
  2. Login or create an EDDMapS Midwest account and submit a report
  3. Contact the City of Northfield Street & Parks Department

Treating trees and preventing emerald ash borers 

Rainbow Treecare is offering Northfield residents a discount on treatment for trees on private property that are at least 10 inches in diameter and in good physical condition.

Northfield discount program for emerald ash borer prevention

Biological controls of Emerald Ash Borer: Minnesota Department of Agriculture

How to protect ash trees (PDF)


Emerald ash borer in Minnesota: University of Minnesota Extension

Emerald Ash Borer Program: Minnesota Department of Agriculture

Invasive Terrestrial Animals: Minnesota Department of Natural Resources

Minnesota Invasive Terrestrial Plants and Pests Center: University of Minnesota

Animal and Plant Health Inspection Service: U.S. Department of Agriculture

National Invasive Species Information Center: U.S. Department of Agriculture