Riohog and Yokel Matt. I'm told it is a moth which lays an egg in the folds of the leaves of onions , leeks etc which then burrows down, as a grub, to feed on the outer layers. Typically you get horrible brown streaks through the flesh and basically the bulb is mush. I'm of a frame of mind to do as you have done in that another rotation might work, but how do you stop a moth?