The gypsy moth problem where I'm from seems like it could become genuinely catastrophic in a few years. That or we figure out how to seed clouds with BTK /s
Recently moved from a town with an infestation. Returned a week later, and no exaggeration, 90% of the leaves in my neighborhood had been chewed away. Even ones where residents had taken steps to protect the tree. I'm not old but I haven't seen devastation like that from an invasive species here in Ontario before.
I saved my beech tree by wrapping the trunk in burlap starting mid-may, and then burning it/squishing all the (thousands of) caterpillars under it on a weekly basis. It has been traumatizing, but my tree is fine. I also sprayed BTK on my small fruit trees and they have been unaffected. So it can be done... but it is time consuming and disgusting.