You can use BT, bacillus thuringiensis. It is a non-toxic way to treat for caterpillars. IT's available at most garden centers, though it can be a little hard to find when there's an outbreak (like the current winter moth caterpillar infestation).

It's easy to apply with a garden hose-end sprayer - you can't reach the tops of very tall trees this way, but you can treat enough of the tree to prevent complete defoliation. I haven't noticed that winter moths specifically attack rose of sharon, but I don't have any of those in a prominent sport. They (winter moths) certainly like maples, cherries, sweet gum, and blueberries.

You may not be able to get a tree guy to come at this point, so calling around to find BT may be your best option, especially if you are interested in a non-toxic approach.

Here is a link that might be useful: bt at cornell

Hi My 2 cents?

Maples can handle a lot of caterpillar chewing and you have to realize that the birds will eat a lot of caterpillars.
If it were something you were growing to eat or something very expensive you could not live with looking ragged then yes BT is the answer. I find that if I wait for nature to address my problems I can be assured something will come along and eat the caterpillars. In my case it is wasps.. I do admit I spray BT on my broccoli and ears of corn.. Because the worms crawl in and they are just gross!!.. But on my cabbages and also on my ornamentals I let nature supply the answer. Mystic is zone 7?? I have got to move to mystic.. LOL