What can I do to stop the spread of ash rust ?
Williams County North Dakota
Ash rust is caused by a fungus that alternates between ash trees and cordgrass (in the genus Spartina). Controlling cordgrass may be difficult to do. A fungicide containing the active ingredient myclobutanil may be used to prevent future infections of ash trees. However, usually ash rust doesn't cause damage to the tree, other than aesthetic damage.
Best wishes with your tree.