Curly Caterpillar...how do I keep them away

Last year my outdoor girls were over run with these caterpillars, Curly I think they are called. I believe the white butterfly's we see flying all over are place are responsible.
Bought some "Safer Brand caterpillar killer" but would rather find a way to stop them before it gets to that stage.
I've heard a garlic type spray applied regularly will do the trick.

Any thoughts?