Hi Charles
we went to the local horticultural soc for a talk on organic gardening and we were told about a pesticide that is certified organic called DIPEL . Have you heard/used or considered this I welcome comments and thoughts about using this on the brassicas when and if the caterpillars appear. Or should I just try opinion garlic chilli spray??
I tried it to control fungus gnats on indoor chilli plants. It stinks of blue cheese. I have no idea if it is appropriate for your use. And it is not cheap.