I have got my best results from sowing all my brassica directly into the allotment, in a seed bed covered by a mesh tunnel.   The hoops are pieces of strong hose slipped over canes stuck in the ground - durable, and no problems with cabbage root fly, or flea beetle.

• Slugs deserve a page to themselves!
• Caterpillars
  • Growing under fine mesh stops butterflies getting in!
  • Planting a few Tagetes/French Marigolds is supposed to confuse the butterflies.
  • When you see the Cabbage Whites fluttering around the allotment, you've almost certainly got their eggs, and very soon the caterpillars.   Go round crushing the eggs (underneath the leaves) and the caterpillars - very satisfying!
  • If prevention hasn't worked, I have occasionally sprayed with derris, on a dry day.
• Whitefly - recent mild winters have been good for these tiny flies, and all the plots on our site are infested.   They seem to be go for my kale first, and spread from there to the brussels sprouts.   They don't do much damage themselves, but the drops of sap they leave on the sprouts grow black mould, which can be hosed off.   Clear over-wintering brassicas before you plant out next year's crop to break the insect's life-cycle.   I'm going to try yarrow and phacelia, to attract wasps which parasitise the whitefly.   HDRA factsheet
• Mustard - I have read somewhere that
  • planting 1 row of mustard 15 days before the cabbages are sown,
  • planting 1 row of mustard 25 days after the cabbages are sown
  • for every 9 rows of cabbages
  keeps your cabbages clear of pests. This was researched in Bangalore - I wonder if it works in Leeds?
• Club Root - if you haven't got it, don't get it!   Be very careful who you accept brassica plants from.   I have club root on one of my half plots, but so far it has not been a major problem - it is manageable, with good crop rotation and liming the bed before the brassicas go in.   Some other ideas -
  • grow your seedlings to transplanting stage in pots of bought-in compost - they're supposed to develop a strong enough root system to cope with clubroot;
  • put a little lime into the hole when transplanting their brassica.
  • or the old-timers' way - place a 1 inch cube of rhubarb in the soil underneath your brassica when you transplant them to their final position; minimum effort, nil cost - nice idea!

If you have any other ideas, let me know please - use the Guest Book link above.