Should I Treat My Ash Tree?

Boy did I get this questions a lot last year. And it is a very valid question to be asking. However, it is not a question with a simple ‘Yes’ or ‘No’ answer. When deciding to treating your ash tree to protect it from Emerald Ash Borer or not, several things need to be considered. There are a few key questions you need to ask yourself before making that decision. There is no right or wrong answer. It is ultimately your decision based on your values and financial abilities. Following these tips will help with that decision:

Question 1: Do I have an ash tree?

OK, this one seems very obvious. But I can tell you of numerous times where someone thought they had an ash tree but didn’t. Not everyone is an expert at trees or plants. And that is OK. I’m no expert at taxes, that why I have an accountant. So yes, verifying and knowing how many ash trees you have before you start is a very important step.

Question 2: Is my tree a good candidate for treatment?

Emerald ash borer treatments must continue indefinitely. Stopping treatment at any point in the future puts your tree at risk. Avoid treating trees with the following attributes (But still answer question 3 after this):

  • Very old and declining ash trees

    • Ash that have the white fungal spots on the bark (Fomes, see picture) are in decline. They will likely die soon or start to break apart anyway. So it may not be the best decision to treat those trees.
  • Very young and small ash trees

    • Avoid treating any ash tree under 10 inches in diameter at 4.5 feet off the ground. Those trees are about 20 feet tall or less. The direct injection of those small trees is very hard on the tree. Plus, you may be better off ahead with quickly removing and replacing with a difference species with such a small tree.
  • Trees with large defects, splits, or decay

    • Trees with the Fomes decay (see picture), large splits, or other defects will not live a long life. Plus, those trees may not accept the chemical as well as a healthy tree. So you could invest time in money into a tree that will die soon anyway or still die from emerald ash borer even if treated.
  • Trees in Poor locations

    • Consider removing trees near powlerlines. Again, they will be open to other pests and diseases due to the stress and are really in the wrong spot since they interfere with the utilities.

All other trees that are healthy, built of good structure, and are in prime locations can be considered to be treated. Excellent candidate trees fro treatment are those trees that are in the 16 to 24 inch diameter range (diameter at 4.5 feet off the ground). The decision to treat these trees or not comes down to the next question you need to ask yourself.

Ash Fomes looks like blobs of white marsh-mellows coming out of the thicker bark on trees. It is the mushroom of the decay fungi deep in the wood.

Fomes white rot decay in an ash tree. This is a sign of internal decay. Avoid treating ash with this disease.






Question 3: How valuable is the tree to ME?

Answering this question for yourself will be the toughest part of this process and a question I make sure all my clients know. When it really gets down to treating for Emerald Ash Borer, there is no ‘Right’ or ‘Wrong’ answer. The treatments (when done correctly and professionally) are upwards of 99% effective at protecting an ash tree from Emerald Ash Borer. So its not a matter of if it will work, but how much are you willing to invest into keeping the tree alive. Once you know the answer to this question you’ll essentially have your answer of if you want to treat or not. If you’re still unsure or have multiple ash trees on your property, click HERE to go read a blog article I wrote on managing emerald ash borer on large properties.

Question 4: Should I wait to treat my ash tree?

I get asked this question a lot. If you live in Sioux Falls and the tree is valuable to you, No, waiting is not a great idea. According to the state department of agriculture, the emerald ash borer population will peak between 2022 and 2026. That is when the mass die-off of ash will happen in Sioux Falls. Here’s why waiting is not a great idea:

  1. It takes 2 to 3 years for a population to build in an ash tree before the tree starts showing signs of decline. By that time, a lot of damage will have occurred to the tree. It is way easier to keep a tree alive and healthy and have the tree ready and waiting full of preventative insecticide rather than treating after its already infested.
  2. Treatments into dying and highly infested trees are not as effective as preventative treatments. There is more risk involved.
  3. The beetle causes damage to the tops of the tree and starts killing off large branches. If you wait and those die, but then save the tree with treatments, those branches will not come back. New branches and limbs will have to re-grow. This will lead to additional expenses to prune out the dead material, increase the risk of those limbs (both dead and new) breaking out and causing harm to people and/or property, and will open the tree up to other pests and disease that may kill it.

The bottom line is that we should not be treating trees of low value, sick or damaged trees, or small trees that do not truly provide a benefit that cannot be replaced within a few short years. Of course, this decision is ultimately yours to make. I have treated trees that I personally thought were not great candidates for treatment. But they were not my trees, and the tree owner knew the facts and still decided to treat the tree. And that is acceptable. That is why there is no wrong or right answer to treating a tree, it depends on your values and financial abilities.