Carrot fly are attracted to the smell of carrots when you thin them out so once that is done you should be ok a little while later. If however they grow in a raised bed, the flies don't seem to be able to get up to them potty - if you know what I mean.

old fashioned remedy/ if you get an hessian sack and sprinkle a few drops of parrafin on the sack and drag it over the tops. but it really needs doing just as the greenery is coming through.good luck.

I'd leave the protective covering on, if I were you, Cochrane, because the little blighters are a hell of a job to keep out of your carrots, especially after you start pulling them. I watched Gardeners' World a couple of weeks ago (before it had to make way for all this tennis stuff!) and Monty Don suggested spreading the seed out over a wider area, not planting in rows, so that you don't have to thin the carrot plants out. I thought that was a good idea, because i have some carrots in a raised bed as well as in the ground, and some of them have carrot fly, regardless of the fact that I haven't disturbed them at all! Good luck with the carrots!! Annie (Cumbria)

Meant to say I know it sounds potty!!