Answer: Unfortunately, based on your description I am not certain what insect is bothering your tree. It might be bagworm, if the caterpillars are making little bags out of the foliage and then hang on the tree. But you must have a definite identification of the pest before you can determine how to treat it.
I strongly recommend you consult with your state extension service to specifically identify both the plant and the pest. Based on knowing that, they can give you the most up to date information on what to use and how/when to use it for best results.
Here is their web site with contact information including their 800 number:
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