I have had the dreaded fly from year 1 of my venture into growing veg, year
2 was the same and it nearly put me off growing the things.
Year 3(last year) I made a timber frame and covered it with pvc around, not
the top as water will not get through. I had no fly and someone here
suggested that it might be because the fly and its larvae died during
winter. I tested this year. I sowed seeds in the frame and a few in open
ground.

The carrots in the frame are perfect whereas the ones in open ground are
riddled with the thing.

To me this is case proven though when I first heard of the barrier method I
was very sceptical.(Isuppose some wiseass is going to make a joke about
barrier method)

It's a faff and expensive making the frame but a carrot fresh out of the
ground is something to write home about, and the frame will last a few
years?

Baz