Carrot fly Psila rosae

Look for

Carrot flies, also known as carrot root flies, infect their host plant's roots causing widespread damage to crops. The damage is caused as the fly larvae feed. Signs to check for are leaf discolouration, and holes or tunnels in the carrot. The holes often turn a rusty colour due to a fungal disease called carrot or parsnip canker which commonly infects the damaged area.

Plants affected

• Carrot flies are a major pest of the whole carrot family. The main host plant is carrots but they also attack celery, celeriac, parsnips and parsley.

About Carrot fly

• Adult carrot flies are part of a group known as stilt-legged-flies. They have long orange legs, a black body and a red/brown head. They're about 4-5mm long and poor fliers.
• The larvae of the carrot fly are the major cause of plant damage.
• They are maggot-like in appearance, growing to about 10mm in length and are creamy yellow in colour.
• Carrot fly pupae are brownish yellow in colour and are found in the soil.
• Carrot fly larvae often cause widespread damage since they move through the soil feeding on different roots.
• Adult carrot flies overwinter below ground and emerge in the spring to mate.
• The first generation of eggs are laid into the soil surrounding the host plants.
• A second generation emerges in July and August. It's this generation that overwinters in the soil.
• Occasionally there can be three generations a year if environmental conditions are favourable.
• If carrot or parsnip canker spores are present within the soil, they can often infect the areas where carrot root fly larvae have been feeding. This causes a rust colouration of the affected areas.

Treatment

Chemical

Products containing the following chemical ingredients are all effective on Carrot fly

• There are no approved insecticides currently available to amateur gardeners.

Note: It is important to read manufacturer's instructions for use and the associated safety data information before applying chemical treatments.

Organic

• Regular checks for damage or infestation.
• Crop containment, for example, covering plants with a fleece barrier.
• Choose growing sites that are fairly open and exposed.
• Remove damaged plants to reduce the smell of carrot which attracts the flies.
• Companion plant with strong smelling plants to mask the carrot smell, such as onions.
• Avoid sowing susceptible plant seed during the early spring and late summer when carrot flies will be laying eggs.
• Thin seedlings in the evening when adult flies are less active and then destroy all thinned plants.
• Firm the soil around the plants after thinning as this deters the flies from laying eggs.

Prevention

• Check the crop regularly for signs of infestation and promptly remove any affected plants.
• Grow less susceptible varieties, such as 'Fly Away' and 'Resistafly', which are low in phenolic acid.
• During the winter, thoroughly fork through the soil where susceptible plants will be grown. This should expose overwintering carrot flies to frosts and predators.