Photo credits: Brian Sullivan, USDA APHIS PPQ, Bugwood.org; R. Jeanette Martin, flickr.com and used with permission via Creative Commons license 2.0; University of Minnesota

tree and park bench icon

1 million

Number of ash trees in yards, parks and streets throughout Hennepin County

emerald ash borer icon

100 percent

Number of ash trees that are susceptible to emerald ash borer and will die unless treated

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15 miles

Most residents live within 15 miles of an infested ash tree.

See where emerald ash borer has spread in Hennepin County (GIF)

Trees provide many benefits

  • Protect air and water
  • Shade homes and help to conserve energy
  • Provide habitat
  • Cool our streets and cities
  • Make our communities healthier
  • Reduce stress levels

Identify

There are several varieties of ash trees in Hennepin County – green, white and black – and all are susceptible to emerald ash borer.

Look for the following characteristics to determine if your tree is an ash tree:

ash tree branches

Branches grow directly opposite from one another.

ash tree leaves

Compound leaves, or multiple leaves on one stalk joined to a branch. Leaves commonly have 5 to 9 leaflets.

ash tree bark

Bark with diamond-shaped pattern.

ash tree seeds

Seeds are oar-shaped samaras that typically hang in clusters.

Resources to identify ash trees

Photo credits: Lindy Buckley (ash leaves); Paul Smith of the Duncannon Appalachian Trail Community (ash tree bark); a200/a77Wells (ash seeds)

Signs of infestation

The following signs may indicate that an ash tree is infested with emerald ash borer.

emerald ash tree

Leaves on the top or one part of the tree start dying.

sprouts growing from a tree base

Sprouts growing from the roots or base of the tree indicate it is stressed.

tree with signs of woodpecker activity

Increased woodpecker activity with sections of the bark stripped away.

holes in an emerald ash tree

Adult beetles leaving the tree create D-shaped exit holes.

signs of larvae feeding

Larvae feeding on the tree's tissue leave a serpentine pattern underneath the bark.

 

Preserve

Treatment with an insecticide is an option to preserve ash trees of high value. See our decision guide for managing ash trees (PDF) to decide what approach to managing ash trees works best for you.

arborist treating an ash tree

What you need to know

  • A healthy, mature ash tree may be worth saving. The tree should be at least 30 inches in circumference (or 10 inches in diameter) at chest height and of value to the property owner.
  • Ash trees within five miles of emerald ash borer infestation should be treated.
  • Preservation treatments must be administered by a certified arborist every two years in late spring. Cost is typically $100 to $200 per tree but varies depending on the tree's size.
  • Hennepin County recommends using a trunk injection of emamectin benzoate (commercial name Tree-age), which is an effective treatment option. It is not a neonicotinoid, which has been shown to negatively impact pollinators.

How treatment works

Learn how treatment works and how to decide if it's the best option for your trees.

Work with an arborist

Whether you are treating or removing your trees, you should work with an ISA-certified arborist. These arborists are trained in proper tree care by the International Society of Arboriculture.

Photo credit: R. Jeanette Martin, flickr.com and used with permission via Creative Commons license 2.0

Remove

Any ash tree not being treated will eventually need to be removed and disposed. A dead tree should be removed before it becomes a hazard.

removing an infected ash tree

What you need to know

  • If you decide to proactively remove ash trees, remove them between October 1 and April 30 to avoid the season emerald ash borer is active and in flight.
  • Trees should be removed by a reliable and insured ISA-certified arborist. Find an ISA-certified arborist near you.
  • To help reduce your individual costs, work with your neighbors to hire a company to remove trees on multiple properties.
  • Dispose ash tree waste at yard waste sites within Hennepin County.

Replant

Trees provide numerous benefits including improving air and water quality, reducing soil erosion, increasing wildlife habitat, providing savings in heating and cooling, and improving health. So planting new trees in place of any you remove is a great idea.

replanting a tree

What you need to know

Photo credit: University of Minnesota

This resource is part of Hennepin County’s effort to maintain a healthy tree canopy and increase awareness about the threat emerald ash borer poses to ash trees.

Contact us

environment@hennepin.us
612-348-3777

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