I apologize that no one has responded to your question sooner. Different experts come online at various times. I just came online and saw your question. My name is ***** ***** I’m a biologist with a special interest in trees. I'm sorry to hear of this problem.
Unfortunately, we have reached the time of year when bag worms can't be controlled. In August, they form cocoons,and pesticides can't reach them. Once they form cocoons, the only thing you can do is pick them off by hand. That's impossible when dealing with numerous trees or large trees. They will stay in their cocoons until next May. When they emerge, it's time to spray with bifenthrin or permethrin. These should be available in a garden shop or nursery. If you don't eliminate them in the spring, they will mate and the next generation begins. The only time they can be controlled with insecticides is from May to July. If you have more questions, let me know in a REPLY. I hope you can get the bag worms under control next spring.