Ash trees

Each spring, as a master gardener, there is one particular question that I get quite often. “My ash trees are losing their leaves and so could it be Emerald Ash Borer?” Generally speaking, no. Emerald Ash borer is now active and in fact, is active between May 1-Sept. 30. The winter months, there is lower activity but even though there may not be activity, you can still potentially spread the pest by our own actions.

Let’s first tackle what happens with our ash trees at this time of the year that makes things look so worrisome. Ash anthracnose, which is a fungal problem in ash trees, often makes itself known about this time of the year. This disease (not an insect) will cause ash trees to lose their leaves. There are times that even without the disease ash trees are known to shed some of their leaves. This also generally happens in the spring time or very early summer. This disease, along with the tree shedding some of its leaves, is nothing to worry about if your tree is a healthy tree and is not a tree that was just planted. You do not need to treat the trees that have ash anthracnose. The smaller trees may have some problems making it through the winter if they lose all of their leaves but I am hoping that in our community we are no longer choosing to plant ash trees and are looking for other trees to plant.

Emerald Ash Borer will most often cause ash trees to lose the leaves on the tree canopy which is the very top of the tree. You may see more woodpeckers hanging around the trees as well. We do not have Emerald Ash Borer in Lyon County. The counties that are nearest to us with Emerald Ash Borer are Brown and Nobles counties and of course, the city of Sioux Falls. The two newest counties that have been quarantined for Emerald Ash Borer are Mower and Rice counties.

According to My Minnesota Trees, the best way to handle ash trees at during the more highly active time is to not remove ash trees or any other part of the tree. If there is a need to have ash trees taken down or cleaned up after because of storm damage, it is best to chip the outer 1 inch layer of the bark and wood while it is still on site and remove to a place where the tree waste can be processed. We don’t really have any areas that process tree waste so the better bet is to not remove it from the area where it fell and make sure that the chipped wood is covered under a sealed tarp or something similar.

It is important to note that Emerald Ash Borer can infest a tree at least a year with the larvae moving about the tree and then after that the tree can possible show no outward signs of being infested by Emerald Ash borer for up to three to five years. The key with ash trees is simply do not move any part of them. If you have wood left over at your campfire, leave it for the next person. It is activities like this that ends up spreading Emerald Ash Borer.

If you suspect that your ash tree has Emerald Ash Borer, is it best to call the Minnesota Department of Agriculture so that they can check out the situation. Contact the Minnesota Department of Agriculture’s Arrest the Pest hotline (888-545-6684; arrest.the.pest@state.mn.us). Note the exact location of the tree and take a digital photo if possible.

Homeowners can use insecticides if the dieback in the canopy is less than 30%. If canopy dieback is more than 30%, then the tree will have a hard time moving the insecticide through the tree. If you are worried about your ash trees, you can hire a licensed professional to help you. There are two treatment styles that can be done before Emerald Ash Borer infects a tree and these are: tree trunk injections and soil/root drenching. Keep in mind that these treatments are expensive!


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