The Dangers And Costs Of Infested Ash Trees

Credit: Joseph O’Brien, USDA Forest Service,

The emerald ash borer (EAB) will kill nearly all of Wisconsin’s ash trees that are not protected by insecticides. To help the public understand why it’s important to act against EAB, the DNR created a publication aimed at homeowners that addresses the dangers and costs of infested ash trees. Urban forestry professionals may wish to share this flyer with those who ask questions on these topics.

The key message of the publication is this: It’s crucial to decide ASAP whether to protect your ash trees with insecticides or have them removed. Either way, time is of the essence. If you delay in treating your ash trees, the treatment may be less effective. And if you wait to remove them, removal costs will be greater and safety hazards will only get worse.

What Makes Infested Trees So Dangerous?

The structural integrity, or strength, of ash branches and tree trunks begins to decline as soon as the tree becomes infested and the wood begins to dry. Lower moisture content increases the risk of branch and trunk breakage, and the timing of breakage is usually unpredictable. Infested trees may also have total trunk failure soon after death, further increasing the chance of dangerous impacts to people and property.

Why Is It More Expensive To Remove A Dead Or Declining Tree?

Credit: David Cappaert,

Dry, weakened trees pose an increased safety risk not only to pedestrians and property, but also to arborists. Many professional tree services won’t let their arborists climb trees that show even 20% decline from EAB, so removing them often requires the use of expensive equipment. Removing an infested tree may cost twice as much as removing a healthy tree, and removing a dead tree may cost three times as much.


If you are interested in treated your ash trees against EAB, check out the recently updated insecticide guides by the University of Wisconsin-Madison Extension. One guide lists options for homeowners and the other lists options for tree care professionals.

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