Cabbage worms

Cabbage worms have always been a problem for me. This year I chopped the tops of the garlic I was harvesting and made a circle around the base of each brocolli and cabbage plant, about 6 inches out from the stem. I thought well it certainly can't hurt. And I accidentally planted my tomatoes in the next row where the prevailing wind carries the scent of the tomatoes over the cabbage types. I looked for cabbage worms in the past few weeks and picked off about 6 total from 2 dozen plants. Today I am packaging brocolli for the freezer, haven't seen a worm and I always look very carefully. I'll try this next year too, I don't know which thing worked but something did.