For the second consecutive year my carrot crop has been destroyed by root fly (not grown in the same area of the vegetable garden this year). Adjacent rows of parsnips were unaffected last year, but I’m not sure if they are affected this year. Does the pest persist in the soil ? I don’t plan to grow carrots next year, but is it likely to recur when I try again or is there anything that can be done to prevent it?
The best solution is a carrot fly fence, 60- 70 cms tall made of polythene or horticultural fleece and buried to prevent gaps and with overlaps where sheets join. It is best made in a long narrow shape, rather than a square, or broad rectangle. So that the flies cannot fly over the top.