Allium leaf miner
I have an allotment in Nottingham and this year my crop, and many others on the allotment site, have had our crops of onions and leeks devastated by a fly of some kind.
I have investigated the cause and on checking the RHS website it appears to be Allium leaf miner as the photograph on the site exactly matches our leeks and onions. The pupae can be found in the body of the leek where I understand that if it were leek moths that were causing the problem the pupea would overwinter in the soil.
My questions are is there any treatment to prevent the crop devastation in future years other than covering the crop? Are there any companion plants that may confuse the fly and prevent them from laying their eggs? Or should we just stop growing alliums?
Any advice on this would be greatly appreciated.