I sowed Red Pak Choi, Khol Rabi and Curly Kale directly in the no-dig bed this spring, as my replacement greenhouse was not ready.
The pak choi have been severely affected by flea beetle, but the other brassica seedlings are completely untouched by the pest, even though they are only 30 to 45 cm away from the pak choi.
This reminded me of an article I found last year regarding experiments to avoid cabbage root fly, which was quite a problem last year: http://sciencenordic.com/pull-push-and-kill-cabbage-root-flies
Kev.