Carrot flies are on of the most troublesome carrot problems.
The small greenish-black carrot flies lay their eggs on the 'collar' of young carrots in summer.
These eggs hatch into legless, elongate, yellow larvae, which enter the skin of the carrots and by continuous tunnelling cause rust- like patches to appear.
At this period the foliage of the carrot plants will wilt and die away.
When full grown the carrot fly larvae enter the soil and change to brown pupae, which hatch out into carrot flies at the end of July and early August.
Eggs are again laid and the larvae again enter the roots, but the plants are now stronger and able to withstand the attack better.
The presence of the carrot fly maggot is, however, revealed by a premature turning of the foliage to the colours usually associated with the autumn.
When full grown they again leave the roots, pupate in the soil, and there remain throughout the winter till the following spring; then the carrot flies hatch out.
When thinning out the carrot crop every care should be taken not to injure those roots still left in, otherwise the carrot flies will be attracted by the smell.
When once the crop is attacked, little can be done, except the careful
pulling and destruction of wilting carrots. An good repellant to keep
carrot fly away is Gamma Dust.
Carrot Fly - Information, Control, Treatment, Advice about carrot flies