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How to Protect Carrots from Carrot Fly

Written by Tildenet Marketing


Posted on 15 March 2021

What is carrot fly?

If you have yet to experience that awful sinking feeling of lifting carrot after carrot riddled with dark crevices, tunnelled out by the dreaded carrot fly larvae, then consider yourself lucky.

Carrot fly is a bug which lays their eggs in the soil around carrots. The adult carrot fly is approximately 9mm long. It is a slender, metallic, greenish-black fly with yellow legs and head. Larvae are creamy white, tapering maggots. When the eggs hatch maggots begin to eat their way into carrots leaving black holes. The black holes then become an invitation to diseases. The larvae that damage the roots can continue to feed through the autumn into winter, moving between plants.

Carrot fly also affects other vegetables in the parsley family, such as Parsnip, Celery, Dill, Coriander, Fennel and Celeriac. They live in bushes, hedges, trees and thrive on allotments where members of the carrot family are planted close together year after year.

At what stage should I protect my carrots from carrot fly?

There is a lot you can do at the planting stage to ensure you get a healthy crop. With other veg you can wait until they are ready to fruit to use plant protection. Carrots need netting at an earlier stage and it’s no ordinary netting as carrot flies are tiny! One option is covering the carrots with a Fleece Blanket immediately after sowing. The other is by putting a Micromesh Barrier around them after the carrot seeds have been sown. As the carrot fly moves around at ground level the micromesh barrier is super-efficient at keeping the fly at bay as well as protecting your crop from harsh winds.

How do you protect carrots from carrot fly?

  1. Make sure to avoid using previously infested ground. Carrot fly larvae can survive through the winter. So, rotate your crops and avoid re-sowing any vegetable from the Parsley family (see above)
  2. Sow later to avoid sowing during the main egg-laying periods, which are (for most parts of the UK): mid-April to the end of May & Mid-July to the end of August.
  3. Sow disease and pest resistant varieties such as Fly Away F1 and Resistafly F1, available from garden centres and online seed suppliers.  
  4. Sow thinly to avoid ‘thinning out’. Thinning seedlings causes the leaves to bruise which emits the scent of carrots into the air which attracts the carrot fly. Thinning out is necessary as carrots crowd each other if not. This results in a crop of scrawny carrots.
  5. Thin out or harvest on a dry evening with no wind – or use scissors so that no bruising of foliage occurs (which will release scent attracting the carrot-flies)
  6. Try companion planting - we have been asked do marigolds deter carrot fly. The answer is Yes! Growing varieties of pungent Rosemary, Alliums, Sage or Marigold provides a deterrent/’smokescreen’
  7. Grow your carrots in a tall planters - for example the Carrot Patio Planters
  8. Lift main carrot crops by Winter, especially if any are infected – don’t leave them in the ground to serve as food for overwintering larvae.
  9. And lastly you may want to know can I eat carrots that have had carrot fly? The answer is yes but you may not find them to be worth the effort. They will be full of holes which you can cut away but you may find they are more hole than carrot!

To find out more about carrot fly, and the other pests that may arrive in your garden check out Pippa Greenwood's excellent RHS book for plant by plant advice on Pests and Diseases

Have you any experience of carrot fly damage? What do you think went wrong? Please let us know your thoughts using the comments section below. 



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