Today 
Creamy-yellow larvae hatch from the white eggs of the carrot fly, Psila rosae, and tunnel into the roots of carrots and other related plants, such as parsnips and celery. The damage creates brown scarring on the exterior of the taproots. Damaged roots are then susceptible to secondary rots. Sometimes the foliage turns yellow and plants might even die.
Solution
Organic
Sow carrots after late-spring to avoid the first generation of carrot fly larvae. Harvest the roots by late-August, before the second generation of larvae emerges.
Carrot fly can detect the scent of carrots from a mile away; sow the seed thinly, as the process of thinning the seedlings releases the carrot's scent. Plant strong-smelling crops, such as garlic, onions, shallots and leeks adjacent to the carrots.
Follow a strict crop rotation plan, avoiding growing carrots on the same site in consecutive years, and place horticultural fleece over the seedlings, which will provide a physical barrier against the pest.
Some carrot varieties - 'Resistafly', 'Sytan' and 'Fly Away' - are less prone to attack.
