Carrot Fly Monitoring

Carrot fly females lay eggs near the stems of plants in the carrot family including parsnip, parsley, celery and weeds such as cow parsley. The maggots burrow into the roots where their tunnels are unsightly and lead to fungal rots. Organic and garden growers may use either fleece or fine mesh to cover the crop, or a deterrent such as interplanting with onions or a garlic spray.

Commercial growers of affected crops are permitted three treatments per season of the artificial pyrethroid, Hallmark, which they seek to apply only when required. The pest has two generations each year, with the first small peak usually in May and the second main peak in August. The timing of these peaks varies from year to year depending on the weather.

Until last year local growers could obtain a warning from Warwick HRI, based on a computer model using input from weather stations, including Aldergrove. From 2010, Warwick is using data from a smaller number of weather stations in the main carrot growing areas of England and Scotland, so growers in N. Ireland no longer have this guidance.  

CAFRE is conducting regular monitoring of carrot fly in several locations, to inform growers.  At present there are no traps in the triangular area between Dungannon, Armagh and Lisburn. Best results come from crops which are not sprayed with insecticide. On farms where the carrots are regularly sprayed it is rare to find enough flies for monitoring to yield useful results. If you live in this area and grow carrots on a small scale without use of insecticides you might like to take part in the monitoring.

Catching the flies is simplicity itself, with an orange sticky trap erected near to the carrots. Identification is more difficult, because many small, innocent insects look remarkably similar to the carrot fly. We rely on an entomologist at AFBI to identify carrot fly. If you would like to take part please contact Anne Stone at CAFRE, Greenmount Campus on 02894 426 683 or 07500 957895.