I had a little caterpillar problem lat year as well. I think they were a moth caterpillar here.
And I 'think' they may gave been infested from nearby spruce trees, but it's only "thinking".
I'll be interested to hear anything that you might learn
Try molasses. I use Brer Rabbit you can get it at the local grocery store. Dilute one tablespoon in a spray bottle and spray the whole plant at dusk. The moths don't like it, so they stay away. Once you get them, it's too late. Spray when the plant is flowering, that's when they lay the eggs. Every night. You'll be glad you did.