Carrot root fly
Roots of carrots, and related plants parsnips, celery and parsley are tunnelled by slender, creamy yellow maggots. Leaves turn reddish and wilt in sunny weather, later turning to yellow. Roots are riddled with maggot tunnels. Damaged roots are susceptible to secondary rots which can affect their storage in winter.
Cultural measures: Delay sowing until late May, early June. Sow thinly to avoid having to thin out too much. Lift the crop early. Cover developing plants with horticultural fleece to a height of around 18 inches to exclude the low flying adult female flies from laying her eggs on the soil close to the crop.
Consider growing less susceptible varieties of carrot Sytan and Flyaway.
There is currently no chemical control available for this.