As I've said a few times I think over the years on here, never had anything attack my leeks.
Have had a very small amount of rust on a few leeks many years ago, not seen it in recent years.
My leeks are planted in different areas in raised beds around my plot.
I do cover some of them them for a short time when first planted for about a month, just to stop anything trampling or blowing onto them while settling in their watered holes. For the rest of their time until early Spring they uncovered.
Looking like I will be picking some in a few weeks time, they are fattening up nicely.