The most important carrot pest is the carrot fly (Psila rosae). Other carrot pests include the carrot cyst nematode (Heterodera carotae), the carrot aphid (Cavariella aegopodii), wireworms, and cutworm caterpillars.
Carrot Fly (Psila rosae)
The carrot fly is the most significant pest of carrots in our region. It also attacks other vegetables such as celery, parsnip, parsley, caraway, and dill, with damage also observed on beets and cruciferous vegetables. In certain areas, it appears frequently and in large numbers. Besides direct damage in the form of tunnels filled with excrement visible on the carrot root, damage also results from qualitative changes. Carrots infected with fly larvae develop a foul smell and bitter taste, making them unsuitable for use. Such carrots are prone to rotting and decay. Plants attacked by the carrot fly can be easily recognized by their purple leaves, which later turn yellow and dry up.
The carrot fly’s body is black, with a brown head, yellowish-brown legs, and is 4-5 mm long. The eggs are elongated and dirty white. The larvae are milky white, 6-8 mm long, narrower at the front of the body, and wider at the back.
The carrot fly has two generations per year. The first generation appears in early May and June, and the second in July. The second generation is usually more numerous and harmful than the first. It overwinters in the pupal stage in a barrel-shaped cocoon in the soil, or in the larval stage in the carrot root in the garden or storage. Egg laying begins at the end of May. The female lays eggs individually or in clusters on the carrot root collar or the surrounding soil. One female lays about 100 eggs.
Flies prefer to lay eggs in moister areas, sheltered and shaded places around houses, on surfaces more overgrown with weeds, around shrubs, and thickets. Loose soil is favorable for egg laying. After hatching, the larvae burrow into the carrot, usually at the top of the root in young plants, and at all locations in older ones. The larvae bore tunnels of varying sizes depending on their stage. After 3-6 weeks, they complete development, leave the carrot root, and pupate in the soil. A larger number of larvae remain in the soil after the carrots are harvested, while a smaller number give rise to the second generation. The percentage of emerging flies largely depends on soil temperature and moisture.
The larvae of the second generation cause damage from August to September, often on the same carrots attacked by the first-generation larvae. Most individuals of the second generation overwinter in the larval stage in the plants in the field or in storage pits, while a smaller number pupate in the soil. Damage is reduced by adhering to a broader crop rotation, where carrots are sown in the same area only every fourth year.
The infestation is weaker when growing carrots in well-ventilated locations. Damage is also reduced by early or very late sowing of carrots. Since loose, friable soil favors egg laying and infestation, it’s advisable to compact the soil around the carrots to prevent cracks suitable for egg laying. Sowing onions between carrot rows repels flies with its scent. Sources of infestation are reduced by destroying wild plant species from the carrot family within a 1 km radius, and newly sown areas should be at least that far from last year’s areas infested with carrot flies. All plants showing symptoms of carrot fly attack should be removed and destroyed as soon as possible.
On small areas, successful protection can be provided by covering crops with nets. Chemical control must be carried out cautiously and with strict adherence to instructions due to the carrot’s properties of absorbing insecticides from the soil. Carrots intended for baby food should not be treated with insecticides at all. Granular insecticides can be applied preventively by spreading them widely before sowing, in rows simultaneously with sowing, or after germination with incorporation. The entire surface or strips along the seed can be sprayed before sowing with the incorporation of the same type of products. Spraying is only effective if done on schedules based on monitoring fly activity. Prescribed withholding periods may limit the application of certain insecticides at specific times.
