So the cabbage worms are doing what they do best: eating cabbage. We sprayed BT on the cabbage yesterday, and we'll hit the rest of the brassicas today.
I learned from Sandi that Christopher's pool net method is not entirely unique. She uses a badminten racket for cabbage moth control (see below).
We'll be able to save these cabbages, but I felt a blood lust for cabbage worms after seeing the damage. Here's to helpful bacteria (BT) and the good old-fashioned methods, too.