[Silva]

Thought my onions were looking a little peaky this year and not just from the dry weather- had an inspection and saw that they have allium leaf miner. I believe there are two generations a year, one around March and one around October. Last year I only noticed them on my leeks in Autumn (so second generation?) but this year they seem to have hit the earlier crops too. They seem to have hit the red onion sets much worse, in fact they're really shredded with tell-tale vertical tracks through several layers already! Hopefully the garlic will get off more lightly!

Has anybody else noticed this pest become more and more of a problem? Have you found that enviromesh does the trick for keeping it at bay? Or do you have any other tricks? I have decided I will be planting out my leeks with the carrots this year as it is my only enviromesh covered bed!

[Yorkie]

It is has become more prevalent over perhaps the last 2-3 years 

I'm not aware of any treatment or prevention, other than covering.

[JayG]

My experience of it is that it affects leeks the most, chives and garlic hardly at all, and shallots somewhere in between (for the past few years they have started to suffer around now, but recovered enough to crop reasonably well after that.)

Enviromesh does work if used correctly (i.e. no gaps) and there is a suggestion that some quick maturing onion sets can be planted in early May, having possibly given them a head start in pots. Ditto onions from seed, again not planting out until the beginning of May.

[Silva]

Thanks, some really helpful tips there! I may hedge my bets and try a combination of early and later onions under cover. The shallots do look a bit ropey as well but I'll hold out some hope! It's interesting to me that the miner seems to be preferring the red onions over the white ones at the moment...