Usually only find leaf damage when the Fig is about to go into dormancy and the leaves are dying anyway. Is the tree stressed? Short of water, for example?
Early last year I had a lot of trouble with Celtis Leaf Beetle demolishing my fig.
I must admit that in the end, when nothing else worked, I resorted to flyspray.
We have had the occasional infestation of the larvae and if left unchecked they can strip our fig trees. The only effective thing we have found for control is squashing them, if there is a small number, or removing the entire leaf and standing on them. I squash the mature beetles and scrape off the eggs. I haven't found/noticed any beneficial insects interested in eating them. We have miniature figs, so checking them is easy, and the impact of the damage if left unchecked is great.