Carrot Root Fly [Psila rosae ] is a small black fly that lays eggs, which develop into creamy-yellow coloured larvae that damage Carrots and other vegetables like Carrots, Parsnips and Celery. The larvae burrow into the Carrot roots making tunnels.The symptoms can show as rusty brown scars. The damage can become so bad that the carrots become un-edible. An early sign of Carrot Fly activity can be a blue-purple colouring of the Carrot plant foilage. Thee are normally 2 generations a year of Carrot Root Fly, one in May-June and the next in August-September.
How to control
Covering early crops with fleece will help hide Carrots from Carrot root flies looking to lay their eggs. If you suspect Carrot root fly is already present; CARROT ROOT FLY KILLER nematodes can be applied to the soil or raised beds where the Carrots are growing. These nematodes will move through the soil to find the Carrot root fly larvae and will significantly reduce their numbers. The Carrot Root Fly Killer nematodes will remain active in the soil for about three weeks, so repeat applications maybe required and applications should be made for each crop of carrots. There is no harvest interval with nematode applications, as they are harmless to humans .