Tackle powdery mildew
Carrot root fly
Are there rusty brown scars on your carrots and little tunnels mining the centre? If so, root flies ( Psila rosae) have been at work. Low-flying females smelled your developing crop and touched down to lay their eggs in the soil nearby. About a week later, creamcoloured maggots hatched, fed on the carrots then pupated in the soil. You can’t turn back the clock, but you can prevent attacks next year. Harvest the crop as soon as it’s ready – a second generation of larvae hatches this month and you don’t want to leave carrots in the ground to feed them. Remove all old carrot debris and dedicate the patch of land to a different crop next year. Next year, sow on a different spot and erect a fleece barrier against the flies. This can be open-topped as long as it’s at least 60cm high, partly embedded in the soil with no gaps. Some advocate a complete covering, but this makes gardening beneath it tricky. Bio-control nematodes are also available to attack them. At the time of writing I’m awaiting new RHS research on this subject…
TOP TIP Root flies also attack the relatives of carrots, so don’t grow parsnips, parsley and celery where they’ve been.