The devastating effects of Emerald Ash Borer have been sweeping through the county the last few years. I get several calls a week with people wondering if there is a way to save their tree from this aggressively spreading pest. Emerald Ash Borer (EAB) is an invasive insect that tunnels into ash trees cutting off the vascular flow and eventually killing the tree. First found in the United States in 2002, it has rapidly spread through the movement of firewood and lumber. As of 2024, EAB has been found in all 72 counties in the state of Wisconsin. 

All true ash species are vulnerable to EAB regardless of tree health, stand, size, or area of planting. However, some trees are better candidates for treatments (and worthy of the cost) more than others, where initial removal may be the best course of action. Trees already in poor health or of little value should be removed before becoming hazardous. Since the insect cuts off water flow within the tree, the wood becomes very brittle and can easily break in winds or storms. Trees that are not yet impacted, are high value specimens, or play an integral role in your home landscape should be treated. If the tree is already infected, but has less than 50% canopy thinning damage it can be treated. 

Signs of damage include: 

What are my treatment options? The main treatment options include injections (done by a certified arborist), soil drenches or granular products (which usually can be done by homeowners). Soil drenches or granular products can be purchased at most nurseries or box stores and should contain the active ingredients acephate or imidacloprid. Treatments are usually repeated on an annual basis, however follow label directions for full application instructions. If the ash tree is smaller than 47 inches around the trunk at chest height, you should be able to treat your own tree (if desired). If the tree is larger, then a certified arborist should be consulted, as soil drench treatments available to homeowners may not be fully effective. Please note that homeowner treatments should not be used in a woodlot setting. 

Find more information on treatment options here: https://hort.extension.wisc.edu/articles/homeowner-guide-emerald-ash-borer-insecticide-treatments/ 

If you decide that your tree should be removed, it is best to use the wood locally to prevent the insect from spreading. Most people use it for firewood, due to its brittleness. There also may be municipality programs in place for disposal if you are unable to use it otherwise. 

Ash trees are declining rapidly throughout the state and should be protected if possible. Find more information on Emerald Ash Borer here: https://eab.russell.wisc.edu/ 

Heat & Drought Adapted Trees! 

Need to replace a tree in your yard? Tree diversity is important for a thriving green space, consider one of these Wisconsin Native species that will thrive in the summer heat and clay soil: 

Find a full listing here: https://hort.extension.wisc.edu/articles/gardening-in-extreme-heat-and-drought/#plants

Early Bird registration is officially open! Take the next step to become a more successful gardener by learning practical gardening skills and techniques and the science behind why they work.

Foundations in Gardening covers a wide range of topics, including:

Early Bird registration rates are valid from now until Aug. 9. Course registration closes Aug. 24, 2026, or when course reaches capacity.

Something eating your plant? Need help identifying a tree? Interested in the best way to care for your lawn? Submit your questions online!

920-832-4764
Kaitlin.Bricco@wisc.edu

The University of Wisconsin–Madison Division of Extension provides equal opportunities in employment and programming in compliance with state and federal law.