My advice to you is to take a few branches of the plant and the worm that is causing the trouble (Just put this into a plastic bag and close the top.) to your local state extension service (addresses can be found for each state in your phone directory or on the internet). They have people who are educated to recognize the insects and plant symptoms and to advise you as to the best products to use to get rid of the pests. If you don't have an extension service in your community, take the piece of plant, with the worm, to a good plant nursery near your home. They can usually advise you as to what product or method you should use to rid yourself of this problem.
