Last July, either "tent caterpillars" or "orange striped caterpillars" ate some leaves about the 6' tall branches. Not too bad.

This year, again, they attacked, only worse. I'm wondering if there are ways to prevent them from coming back, just like the idea of how pre-emergent does to prevent weeds before they seed? I don't want to KILL them, but just trying to deter them next year. Thanks