Emerald Ash Borer - prevention and management strategies
Peek out your window. If you can see trees, chances are at least one of them is an ash tree. There are nearly 1 billion of these deciduous trees across Minnesota, and they make up 20 percent of the canopies in our cities. But they could soon disappear.
Since 2009, an invasive beetle called Emerald Ash Borer (EAB) has been chewing through the State’s Ash tree population, killing the trees by disrupting their ability to transport water and nutrients. EAB larvae create winding “galleries” in the outer sapwood of Ash trees. That layer of a tree’s tissue is responsible for carrying food from the leaves to the rest of the tree. When that layer is disturbed, canopy thinning and brittle bark occurs.
Once an ash tree becomes infested by EAB, it is often killed in 3-4 years.
The EAB spends almost its entire lifecycle under a tree’s bark, so it can be difficult to look at your tree and easily identify if it is infested or not. If your once-thriving ash tree has developed a thinning canopy, there is a good chance the tree is infested with these invasive beetles.
What do Ash trees look like?
There are several varieties of Ash trees in Scott County: green, white, and black, all of which are susceptible to EAB. For a quick ID card, download Hennepin county’s fact sheet. In general, look for the following characteristics to determine if your tree is an ash tree.
What can be done?
There are two options if you have an EAB infestation: Treatment, or removal.
EAB treatment is possible and suggested if you currently have a healthy Ash tree that is within 15 miles of known EAB infestation. The entirety of Scott County’s boundaries are within assumed EAB infestations. You can check the local status of EAB by visiting the Minnesota Department of Agriculture’s status map.
If you wish to proceed with treatments, it is recommended to hire an International Society of Arboriculture (ISA)-certified arborist to assess and treat your trees, and treatment should be repeated every two years.
The cost of treating an ash tree for EAB in the Twin Cities Metro is typically between $70 and $200. To help offset costs, 35 municipalities in Minnesota, including Shakopee, Savage, and Prior Lake, offer discounted treatments to private property owners. If your city is not on this list, contact your natural resources department or city forester to ask if they have an EAB plan in place.
In cases where Ash trees have already lost more than 50 percent of their canopy and are too damaged to save, removal of the existing tree and replacing it with a new tree is the best option. It is much easier, safer, and less expensive to remove trees while they are still alive, so once you start to notice a change, it is important to act quickly.
Once removal of the infested tree has happened, replace the area with something new! Trees provide a multitude of benefits to our landscape including higher property values, health benefits, storm water runoff reduction, and even energy savings. Mature trees provide shade, which reduces cooling costs in the summer.
In Minnesota’s southeast big woods region—the area of land the Scott SWCD encompasses—Red Oaks, Sugar Maples, Basswoods, and American Elm trees have historical and present-day representation. For a full list of recommended trees, visit the UMN’s page on tree selection and care.
Help limit EAB’s spread.
Don’t move firewood! Most EAB will naturally move only ½ to 1 mile a year from an infested site. But when people transport firewood, they can travel hundreds of miles in mere hours. Don’t transport firewood when you go camping. Buy wood from local sites or from campgrounds that you are visiting.
For more information on Emerald Ash Borer beetles and infestation symptoms, visit the UMN’s page on Emerald Ash Borer in Minnesota.