Some ash trees are beginning to drop leaves. This is an annual occurrence that happens around this time of year and will continue for the next 3 to 6 weeks or so. It is not related to Emerald Ash Borer activity. It is caused by a leaf fungus anthracnose (PDF). It is a temporary condition that, in general, is not harmful to the tree. The trees may produce more leaves later on in the season. We do not do any type of preventative or curative treatments (spraying) for this.