Q. What might be happening to our ash trees? We noticed that a couple of our ash trees are not doing well at all.  I did a quick google search yesterday and found an article you wrote about ash dieback. I’m hoping that’s not what is happening to our trees, but it does look like it. The only other thing that might have happened is that my husband put sterilant down on some rocks nearby last November. Now we are wondering if perhaps the sterilant made its way down to tree roots that may have been growing beneath the rocks?  I believe he treated the whole area with the sterilant, and you can see where the tree trunk is located in relation to the rocks.  If it is in fact a chemical injury to the trees, is there anything that can be done? Ash Decline (disease) or not?  Ash Decline looks just like the trees are not getting enough water. You wont know until you water it (give it some extra water) for a few weeks and find out. Unless you want to pay a big plant pathology bill. A. I don’t think your ash tree has this particular disease. After looking at the pictures you sent, I think it was caused by the sterilant. It’s helpful if you can tell me the name of the sterilant used. Many sterilants are taken up by plant roots. The sterilant damage usually occurs on leaves and stems. On leaves, sometimes they “scorch” (their leaf margins will burn). This is what I think I see. In many cases the leaves turn yellow or become “bleached”. This is the type of “yellowing” I’m talking about. It is not “sterilant” yellowing but this is the color I am talking about.             Tree roots watered by rainfall extend horizontally to about the length of their height. So, if you roughly (visually) lay the tree on its side and spin a circle with it, that roughly extends the length of their roots (with rainfall). Some pine trees I was given to spray with Dicamba, because we saw some dicamba issues on some pine trees when I worked for Utah State University as a Horticulturist.             In the desert tree roots follow water. Wherever water is applied, that’s where you will find its roots if this area is under its canopy. I noticed a lawn under the tree. Did you kill a part of the lawn with sterilant? Many sterilants are taken up by plant roots but this sterilant can oftentimes be seen in the leaves. Dicamba was also used as a sterilant. This is what dicamba damage looks like on pine trees. Shout out to my friends in SLC Utah.             If it is sterilant damage, you can try a couple of things. First try to wash it out. It may or may not work. Putting a lot of extra water in that area may flush the sterilant out. Just remember to give a day or so without water to give a chance for the roots to “breathe”. Roots need both air and water to survive.             There is a chance that putting activated charcoal (expensive, activated carbon its called and is specific to the sterilant) may help but it depends on the sterilant used.             When there is consistent rainfall, roots of trees extend all through the soil under its so-called “canopy”. Your ash tree grows in a lawn. Watering lawns is more even, regular, and consistent than rainfall. Ash trees do remarkably well in lawns. In my opinion that is their preferred way of getting water to the roots.             Ash trees infected with ash decline are not getting enough water to the dying limbs.  This disease plugs the water conducting vessels in tree limbs. As this disease slowly gets worse, more and more limbs begin dying because of a lack of water. The homeowner ends up removing the tree because it looks “ugly”.              To see if your tree has this disease or not, give it some extra water once a week during the summer! An extra irrigation during the week tells you if the tree has this disease or not. If the tree does not improve in a few weeks with this extra irrigation, then assume the tree has the disease.             The mistake made by most homeowners, in my opinion, is not removing the tree as soon as they decide one way or another. If you have confirmed this disease, then remove the tree as soon as possible. This tree can spread this disease to other ash trees!