Growing carrots

We have had an inquiry about growing carrots after an infestation of carrot fly.  I do keep moving all veg beds around in rotation to stop a build up of pests. The only way I can grow carrots is by covering them in a sealed cloche using polythene to stop the fly getting in !!! Even ones growing in the greenhouse can be infected although the early Nantes 2 variety seems to do better partly because the door is kept closed as its cold in March. Ive tried carrot fly barriers but dont find they help because Im gardening on a steep slope so the fly is not fooled.

Best of luck

Selina