Carrots in allotments are not easy - there are so many "reservoirs" for carrot fly to overwinter, and so many inviting rows for them to visit.   The fly can apparently smell carrots 7 miles away - an allotment site must be paradise for them.

No one method of protection works on its own - better to use as many as you can, including

• Use physical barriers a fleece or enviromesh tunnel is probably the best alternative, as long as you don't forget to weed and water
• sowing at the right time to avoid egg-laying period, February/early March (under cloches, or in a cold frame) to harvest in July, and July/early August for a winter crop.
• fanatical cleanliness - which rather goes against the grain! - remove affected crops.   That means as soon as you signs of carrot fly in a crop, and before the end of September.   Remove all debris - don't allow any reservoirs for maturing or over-wintering carrot flies.
• Choose resistant varieties.   Choose some for resistance - Kitchen Garden Magazine found Parabel and Yellowstone unaffected by the fly, and Cubic and Fly Away moderately affected.   My fourth year, I actually chose Autumn King, their favourite apparently, to keep the carrot fly population happy and busy - and of course that year, we'd no carrot fly, but vandals destroyed the crop!
• A long list of ideas - the mad, the bad, and a few that may work!

How to - It is as well that fresh carrots are so good to eat!

• Carrots don't like stony or freshly manured beds - but they do like a good deep soil; use a bed which was manured the previous year.
• Sow in shallow drills, about 6 inches apart, and lightly cover.
• Thin progressively until plants are about 2 inches apart - beware, carrots have a strong scent, so this is likely to attract the dreaded fly.
• Keep beds weed free, at least in early stages.
• Don't allow the beds to dry out - water regularly, and lay a mulch on the top soil.
• And good luck to you!

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