leeks
Could someone please tell me what has caused this terrible damage to my leeks, and also those on my friends allotment.
The ones picked in early October were ok, but all the rest are affedted

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Could someone please tell me what has caused this terrible damage to my leeks, and also those on my friends allotment.
The ones picked in early October were ok, but all the rest are affedted
Posts
Think I'd plump for alliums leaf miner with subsequent fungal infection.
I agree. Peel the layers off, one by one and see if you find any small brown/black pupae buried inside which will confirm that it's allium leaf minor rather than leek moth.
Had an attack a couple of years ago about this time of the year but didn't get the problem last year. Crop rotation and/or covering with fleece from mid September are the only controls.