Authors: PJ Liesch, UW Entomology, Patti Nagai, UW-Extension Racine County and R. Chris Williamson, UW Entomology
Last Revised: 04/07/2022
This factsheet addresses some of the most frequently asked questions regarding the treatment of ash trees for emerald ash borer (EAB), and the removal and disposal of infested trees.
When should I consider treating my ash tree for EAB? Historically, treatment decisions were based upon being within or near a quarantined county. However, in 2018 the EAB quarantine was extended over the entire state and most Wisconsin residents now live in counties with known EAB infestations or are close to an infestation. Thus, treatments may be warranted for EAB regardless of location within Wisconsin. Due to the expense of insecticide treatments for EAB, consider the value of a particular ash tree in relation to treatment costs before making any treatments. Proper use of EAB insecticides can help maintain the health of high value ash trees over time. Lower value ash trees and trees in poor health are not good candidates for EAB insecticide treatments.
How do I know if my ash tree has value? Ash trees can be a valuable part of the landscape. A properly cared for ash tree can increase property value, provide environmental benefits such as runoff and erosion mitigation, and reduce electricity costs by shading a home. Determining tree value can be subjective, but several online calculators exist to estimate tree value (e.g., Arbor Day Foundation, etc.).
Qualities to consider when assessing value include (but are not limited to) a tree’s overall health, shape, location with respect to landscape design, and appearance through the seasons, as well as whether or not a tree provides shade. A healthy ash tree that is properly located in the landscape, has a nice shape and good fall color, and provides shade has value. An ash tree that is not healthy due to disease or insects, has poor shape or structural damage, is otherwise unattractive, or is in a bad location (e.g., near a power line) is of lower value.
How do I know if there are ash trees in my area that are infested with EAB? EAB was first detected in Wisconsin in 2008 and has since spread around much of the state. The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) keeps track of EAB infestations in Wisconsin. Visit the Wisconsin DATCP EAB Resource Guide website (datcpservices.wisconsin.gov/eab/)and view the interactive map. You can also contact your local county Extension office to see if EAB has been found in your area.
How do I know if my ash tree has EAB? Symptoms of an EAB infestation can include canopy thinning starting in the upper portion of the tree, epicormic sprouting (i.e., formation of sprouts) along the trunk, bark splitting, and woodpecker damage. These symptoms indicate general tree stress and can be due to EAB. However, they also can be caused by diseases or insects other than EAB. Specific signs of EAB include D-shaped exit holes (~3/16 inch wide) in the bark of the tree, S-shaped larval tunnels and/or larvae (cream colored, up to 1½ inches long) beneath the bark, and adults (metallic green, ~3/8 inch long). Visit the UW-Madison Emerald Ash Borer in Wisconsin website (eab.russell.wisc.edu) for additional information on the symptoms and signs of EAB.
If I decide to treat my ash tree, will I have to treat it every year? In most cases, yes. Most insecticides registered for EAB require yearly applications to effectively protect a tree. Products containing the active ingredient emamectin benzoate, are labelled for two years of protection. Products containing emamectin benzoate are trunk-injected insecticides intended for use by professional insecticide applicators (e.g., certified arborists). Such products can effectively protect an ash tree if the tree is treated every other year.
Can I treat an ash myself or do I have to call an arborist? If your ash is smaller than 47 inches around the trunk at chest height [i.e., 15″ diameter at breast height (DBH)], you may be able to treat your ash tree yourself.
University of Wisconsin Pest Alert XHT1181 (“Homeowner Guide to Emerald Ash Borer Insecticide Treatments”) provides a list of products currently available for homeowner use. If you decide to treat your own trees, be sure to read and follow all label instructions of the insecticide that you select to ensure that you use the product in the safest and most effective manner possible.
In some situations, hiring a certified arborist to treat your ash tree may be more desirable. Professionals have access to specialized application equipment and additional insecticides not available to homeowners. They are also trained to measure trees accurately, and assess the overall health of trees. The Wisconsin Arborists Association website (www.waa-isa.org) has a list of certified arborists in the state.
Note that the University of Wisconsin does not endorse any specific insecticide products or application techniques over others.
Am I allowed to treat an ash tree in my yard between the sidewalk and street? The answer to this question can vary from municipality to municipality. In many cases, municipalities have treatment or removal & replacement plans already in place. Contact your local town, village or city to determine an appropriate strategy for protecting your sidewalk trees from EAB.
How much does it cost to treat an ash tree for EAB? A single tree that is 32 inches around at chest height (approximately 10″ DBH) can be treated with a granular or liquid soil drench homeowner product for about $20-35/year. Larger trees will require a larger amount of product and costs will be higher. Arborist treatment costs vary depending on tree size and location, the insecticide selected, and the application method. Other arborist-specific site visit charges may apply as well. It can be helpful to consult two or more arborists in your area to discuss treatment options and costs. To make an accurate comparison among service providers, make sure you know what insecticide will be used, the method of application, and how often treatments will be made. An arborist may not be able to determine the exact cost of treatment for your specific ash tree without a site visit, but they may be able to provide you with a general cost estimate for a typical ash tree.
Do I have to remove my ash tree if it is infested with EAB? Using protective treatments to prevent an EAB infestation is often the best strategy for managing EAB. However, if a tree becomes infested and the infestation is detected early, you may be able to treat your ash tree to prevent further damage, and help the tree recover. Research suggests that insecticide treatments are significantly more effective on EAB-infested ash trees with less than 50% canopy thinning. Insecticide treatments are not recommended for trees with greater than 50% canopy thinning; these trees should be removed. Trees that become infested with EAB and are not treated will ultimately die and will need to be removed.
How much does it cost to remove an ash tree? Typically, a small (less than 25 feet in height) ash tree may cost several hundred dollars to be removed by an arborist. Larger trees may cost $1,000 or more to be removed. Individual site factors (e.g., proximity of the tree to structures, power lines, or other hazards) can significantly increase the cost of removal. Tree removal costs also may vary from location to location in Wisconsin. Ultimately, removing recently killed trees while they are structurally sound, can be safer and more cost effective. Ash trees are known to become brittle and hazardous relatively quickly, which can increase removal costs by an arborist. See WI-DNR Publication FR-766 “Emerald ash borer: the dangers and costs of infested trees” for additional information on this topic.
How do I dispose of wood from an infested ash tree? If you choose to remove an infested ash tree, check with your municipality to see if a wood disposal or utilization program is in place. If you have a tree removed by a tree care service, the service may be able to handle the disposal of wood from the infested tree. If you decide to use wood from an ash tree for firewood or other purposes, the best course of action is to use it locally. Transporting infested wood risks spreading EAB elsewhere in the state and region. Information about Wisconsin’s firewood regulations can be found on the Wisconsin DATCP Emerald Ash Borer website (datcpservices.wisconsin.gov/eab/).
For more information on controlling emerald ash borer: Visit eab.russell.wisc.edu, datcpservices.wisconsin.gov/eab/, or www.emeraldashborer.info, see University of Wisconsin Pest Alert XHT1181, or contact your county Extension office. For a video demonstration of treating your ash trees using a systemic drench, visit eab.russell.wisc.edu/2014/07/12/protecting-your-tree-from-the-emerald-ash-borer/.