HELP: I have this big bright green nest in my Ash tree!
More than likely, your Ash tree does have Mistletoe. It is all over your area. This particular parasite really only affects Ash and Cottonwood. The parasite lives in the trees and kills the vascular system. On its own, it is a slow mover and a slow killer so your tree is not going to drop dead any time soon. What you see is not the parasite but the fruit of the parasite. The birds eat it and they poop spreading the parasite. We can remove the fruit but it will grow back. Removing the fruit will help slow the spread although many other trees in your area have Mistletoe. And to think, we kiss under this stuff!