I learnt about this over the weekend; thanks for the info Alan.
My leeks on 41A Bluebell South, closest to George Borrow Road got ravaged by something from late August onwards. I thought it was slugs so put slug death down; seemed to improve things a bit, they were getting got from the tops though.
I noticed a few other plots nearby got it too. Alan told me this Sunday it was leek moth; a new pest to me. Apparently, they come out in May/June and August/October and mine onion and leek leaves. No amateur pesticides; only treatment is removal of caterpillars, or prevention by growing under enviromesh.
I know planting carrots in between alliums is s'posed to keep carrot fly off carrots (doesn't work according to some people; but they grow very long rows of carrots). I was wondering if anyone knew whether intercropping with fennel would put them off, or even growing Calendula, Tagetes or Nasturtiums round the edges of the plot. I haven't seen this as a control method anywhere I've looked; is this because it won't work?
Also, I have grown leeks on North side for years without this problem. They were put in "wrongly" by someone else; soil filled in around transplants rather than left with a hole around. Is it location (less moths on North side of Avenues) or not filling in soil that's been key?