If I grow my cabbages and cauliflowers inside a fleece covered tunnel (as opposed to netting) will I still need to use collars?
I don't know for sure, Jesseveve - but I sow all my brassicas under fleece; transplant them into the beds. I've lost no more than a couple of plants over 3-4 years to cabbage root fly.
I'm guessing that the fleece protects them just as the fly emerges from overwintering in the soil - and it has to fly off to other people's plots?
All best - Gavin (Unless you're on the plots next to mine, that is :o )