Posted: 18/07/2015 at 11:57
I did see that RHS stuff, thanks, but it's not a lot of help. I grow onions and shallots from sets, and this can't be safe, as sets produce their first leaf when in the soil. The affected plants were all grown from sets, in a bed that has never had onions in it before, so I don't know where the infection came from.
Luckily I have enough space to be able to comply with this rule, but it's a bit dispiriting, as it may happen again if I don't know how to prevent it. I've already given up on leeks, which used to do very well, because of leek moth that completely ruined the whole crop last year.
But it's swings and roundabouts, I suppose; I have great carrots and beans, and masses of mangetout (which failed last year). We are just eating up the sound parts of the onions as fast as we can before they rot.