Carrot Fly

Carrot Root Fly

Carrot Fly Facts

Common Name: Carrot Fly.

Scientific names: Psila Rosae.

Carrot Fly can affect carrots, parsnips, celery, celeriac and parsley.

Carrot Fly is active from May to October.

Symptoms include:

  • Rusty brown scars ring the tap roots of carrot and other vegetables, making them inedible
  • Tunnels are revealed, often inhabited by slim off-white/yellow maggots up to 9mm long
  • Carrot rust fly larvae cause surface tunnels in roots. Tunnels are filled with a rusty mush and the stiff white maggots. There are no above ground symptoms.

In allotments and gardens the plants often die. The Carrot Fly thrives in these habitats as it likes sheltering in trees, shrubs and hedges. Also, allotments tend to be full of carrot-family crops, grown closely together year after year. When you pull the roots up, blackened surface tunnels, often containing maggots, can be found all over them.

Parsnips are similarly mined by the larvae, especially the 'shoulders' of the root. Young seedlings can be attacked in the leaf stems, as well as the root. This usually kills the seedlings. Celery stems are mined particularly where the stems grow from a crown at soil level. Larvae also tunnel into celeriac roots. Parsley is affected by the larvae killing the thin tap root. If plants die, look for mines with larvae in the crown of the plant.

About Carrot Fly

Carrot Fly Lifecycle

First-generation adult carrot flies are born from pupae from late April to early June. The timing will depend on temperatures in the spring. Newly emerged carrot flies feed and begin to mate. Several days later, they lay their eggs in the soil near to the base of a carrot plant. 

The newly hatched larvae move through the soil to the root system. At first, the larvae feed on the lateral roots, but then they tunnel into the taproot. When fully grown, the larvae pupate, and the second generation of flies emerge from these pupae in mid-July to August and lay eggs. 

Depending on weather conditions, the eggs laid at the beginning of the second generation may develop into the third generation of adults, emerging in early autumn.  

Most second-generation eggs do not reach the adult stage, however. Some reach the pupal stage by the start of winter, while the remainder continues to feed on overwintered carrots until they form pupae in the spring. 

If carrot fly larvae attack carrot seedlings, they are likely to kill them. Once the taproot has started to develop, they cause damage by tunnelling into it, to feed. Research has shown that most damage to overwintering carrots results from larvae that hatch from eggs laid in late July - early August at the beginning of the second fly generation.  

Unless good control is in place at this time, it’s impossible to prevent damage from increasing during the winter months. When there is a third generation, carrot fly activity can extend over several weeks, and viable eggs can be laid. 


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