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April 7, 2015

MADISON -- Emerald ash borer is currently the most damaging threat to trees in Wisconsin, according to state forestry officials, who say the pest could kill more than 99 percent of ash trees in the state.

That would account for more than 725 million trees and make up more than 20 percent of the state's urban forests.

"Many people don't notice that their ash tree has emerald ash borers until it is too infested to save, so it is important to examine your ash trees early and often," says Bill McNee, Forest Health Specialist with the Wisconsin Department of Natural Resources. "Now is a good time to consider insecticide protection, because the treatments are usually done between mid-April and mid-May once leaves begin to return."

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View the slideshow on emerald ash borer.

Foresters recommend that homeowners consider insecticide treatments if they have ash trees in a quarantined county, or outside a quarantine county but within 15 miles of a known infestation [PDF] (exit DNR). Elsewhere in Wisconsin, the risk of trees being infested is lower, but homeowners may still want to treat their trees.

EAB quarantine counties
EAB quarantine counties
WDNR Photo

"Location isn't the only consideration when deciding to treat," McNee says. "For example, the treatments are not practical for woodlot ash trees and need to be repeated every one to three years for the rest of the tree's life." For more information people can check out a UW-Extension publication "Is My Ash Tree Worth Treating for Emerald Ash Borer [PDF]" (exit DNR).

What homeowners should do

If EAB has been found in your local area or you see any of the signs or symptoms of EAB infestation (exit DNR) in ash trees, look for information online or seek advice from a tree care professional. People can search for a certified arborist on the Wisconsin Arborist Association's website (exit DNR). Other businesses also conduct EAB treatments.

"Some of the insecticide products can be applied by a homeowner and others must be applied by a certified professional," McNee says. "Done properly and at the right time, odds are good that you will be able to protect a tree that is currently in good health." Information about insecticide options is on the Wisconsin emerald ash borer website (exit DNR). People who purchase an insecticide and treat their own trees, should follow the product label instructions to apply it properly and safely.

Only ash trees need to be protected against EAB, and not all ash trees are worth treating. Mountain ash and prickly ash do not need protection because they are not attacked by EAB.

Consider the following when deciding whether or not to treat your ash tree.

Signs and symptoms of EAB infestation:

People can stay informed and be on the lookout for emerald ash borer by following these suggestions on the Wisconsin Emerald Ash Borer website (exit DNR). Know where the pest has already been found and look for the signs and symptoms of infestation. Watch ash trees for the following:

Information about EAB, including the known locations of EAB, signs and symptoms of infestation, and UW-Extension treatment factsheets are available online at: (exit DNR).

FOR MORE INFORMATION CONTACT: Bill McNee - Wisconsin DNR Forest Health Specialist, Plymouth (920-893-8543,

Last Revised: Tuesday, April 07, 2015

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