Is butterfly netting the answer...?
Thanks for your enquiry regarding butterfly netting and unfortunately your suspicions concerning this material are with foundation! Although the 7mm mesh netting is small enough to keep out the cabbage white butterfly, it will also exclude a number of bees and other beneficial insects which help with pollination. However, if used exclusively on brassica crops – which do not require the attention of these insects – then the mesh is ideal.
Best of luck with your brassica growing!