One of my trees has, I think, bag worms. It has web like places on several branches and tiny black spots on the leaves. I had them cut off. Is there something I should spray on the rest of the tree to prevent this from spreading?
At this time of year I'm thinking you are referring to fall web worms. These worms build a cluster at the ends of branches. Since they attack only in the fall of the year
chemical control is not warranted. I would do as you have done and cut the web out
and destroy. Be sure to make a clean cut. The leaves on your tree have accomplished much of what they needed to do by now. I would not worry about the
spots on the floiage.