map showing locations of emerald ash borer detections in Wisconsin

Stay informed and be on the lookout for emerald ash borer. / Photo Credit: Wisconsin Department of Agriculture, Trade and Consumer Protection

MADISON, Wis. – The Wisconsin Department of Natural Resources (DNR) encourages property owners with healthy, valuable ash trees to treat them with insecticide this spring to protect against emerald ash borer. The pest is currently the most damaging threat to trees in Wisconsin, killing more than 99% of the ash trees it infests.

A common first sign of emerald ash borer infestation is woodpecker damage created when birds feed on emerald ash borer larvae beneath the bark of ash trees. Treatment of infested ash trees is more likely to succeed if the trees have low or moderate levels of woodpecker damage. Now is a good time to consider insecticide protection because the treatments are typically done between mid-April and mid-May.

Emerald ash borer was recently found in Bayfield and Lincoln counties for the first time, and has become so widespread that treatments are worth considering anywhere in Wisconsin. The highest risk of infestation is in communities already known to be infested or within 15 miles of a known infestation. The risk is lower elsewhere, but the DNR suspects that there are additional undetected emerald ash borer infestations. You can find more emerald ash borer detection information at

Homeowners can apply some insecticide products, and others must be applied by a certified professional. Review the available options before selecting an insecticide and treatment method. Visit the Wisconsin EAB website and EAB Information Network website for more information about insecticides. Additionally, you can search for a certified arborist at the Wisconsin Arborist Association’s website. Other businesses that conduct emerald ash borer treatments may be found online or in a phone book.

Stay informed and be on the lookout for emerald ash borer. Know where the pest has already been found and look for the signs and symptoms of emerald ash borer infestation. Watch ash trees for the following:

light flecking on an ash tree

  • Woodpecker damage called “flecking,” where pieces of bark have been removed while feeding on emerald ash borer larvae beneath the bark. It usually starts up in the canopy and progresses down the tree over the next few years if the tree is not treated.
  • Sprouts growing from the base or trunk of the tree.
  • Thinning canopy with smaller, pale leaves.
  • Small (one-eighth inch), D-shaped exit holes in the bark.
  • Green beetles crawling on the trunk of ash trees during the summer.

Visit the DNR emerald ash borer webpage for more information.

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