[beesrus]

Make sure you don't leave even tiny gaps at the edges of the netting - carrot flies may well be crummy flyers but that doesn't mean they can't walk towards their targets!

That is soooo true with carrots. Almost hermetical sealing at ground level is what is required on allotment sites where colonies have thrived for decades. Think Frodo, Sam and Shelob... there's always a way if the need is great enough.