My cauliflowers were nearly decimated by them. I successfully netted them against the pigeons but was tearing my hair out with the cabbage white. Think I will just not grow brassicas next year.
I'm going to try planting tons of nastursiums in the hope that they'll freely decimate them and leave my brassicas alone. Otherwise I may have to give up on them also. Nothing worse than having pests munch your carefully nurtured plants. I've already lost a few cabbages to slugs
My problem is two fold, White butterfly and Pigeons. This year I covered all my cabbage etc with securely fixed nylon fleece over a made up frame. The fleece was a bit expensive but it has been worth every penny. The frame was made from scraps of wood and rustynails. The pigeons just gave up in the end and I had a certain amount of pleasure in watching the white butterflies get all frustrated then fly off to somewhere else. Both fleece and frame will be good for at least a couple of years yet. Who is very pleased with themselves?