Carrot (Daucus carota) – is a plant of the Apiaceae family (Umbelliferae), cultivated for its thickened root. It is a biennial plant: in the first year, it forms a thickened root, where the reserve substances are stored. In the second year, the plant blooms and produces seeds. It contains carbohydrates, fiber, beta-carotene, sugars, protein, and sodium. The carrot crops can be affected by pests and diseases, against which it’s important to apply the right treatments.

The main diseases of carrots

Bacteriosis

Bacterial soft rot (Erwinia carotovora subsp. carotovora)

The attacked tissue turns into a mucilaginous mass, while the epidermis usually remains intact. The rotting is accompanied by an unpleasant odour produced by bacterial growth. Soft rot diseases rarely occur in the field and are usually associated with excessively wet conditions. In many cases, infection becomes evident only during transport and storage.

Prevention and control measures:

• avoiding clay soils;
• sorting the carrots before storage;
• carrot treatments with specific fungicides.

Bacterial blight of carrot (Xanthomonas campestris pv. carotae)

The disease causes plant yellowing and dwarfing. The disease progresses and irregular, brownish spots appear on the leaves. Elongated brownish spots appear on the leaves’ petiole.

Prevention and control measures:

• avoiding sprinkler irrigation;
• using healthy and certified seeds;
• practicing a rational crop rotation;
• chemical treatments with specific fungicides.

Mycosis

Carrot leaf blight (Alternaria dauci)

Small, brown spots appear on the edges of the leaves, surrounded by a yellowish area, which subsequently leads, in severe cases, to tissue death and complete leaf drying. As a result, the crop appears to have been burnt. Mature leaves are attacked first, being more susceptible to alternaria than young leaves. In general, the root remains unaffected. Affected leaves will fall slightly, making mechanical harvesting difficult.

Prevention and control measures:

• removing diseased plants from the crop;
• destroying plant debris, after harvest;
• chemical carrot treatments with specific fungicides.

Gray mold (Botrytis cinerea)

The attack is present in years with heavy rainfall. The first obvious symptom is the sudden wilting of succulent tissues (stems, roots, and young leaves). If the humidity remains high for a long time (several days), the fungus fructifications appear on the affected tissues as a greyish fuzz. In carrots case, the disease can also develop in the warehouse.

Prevention and control measures:

• avoiding sprinkler irrigation;
• sorting the carrots before storage;
• chemical carrot treatments during the growing season with specific fungicides.

Powdery mildew (Erysiphe umbelliferarum)

Powdery mildew occurs in dry and hot weather. Attacked carrot leaves are covered with a white, powdery mycelium. If climatic conditions are favorable, the affected tissues become necrotic. At the end of vegetation, the mycelium changes color to greyish. Small black dots appear on the mycelium, representing the fungus fructifications. During vegetation, the fungus is transmitted by spores, and from one year to the next, by the fungus fructifications, which survive on plant debris.

Prevention and control measures:

• using healthy seeds;
• destroying plant debris, after harvest;
• chemical treatments with specific fungicides.

Dry rot (Fusarium avenaceum)

Fusarium causes dry rot, generally between the base of the leaves and the top of the carrot root. The affected areas begin to dry out and turn brown. As the attack progresses, the affected parts dry out and harden. Under damp conditions, a pink mycelium develops on the surface. The rot usually starts in the crown area, but can also appear on the root.

Prevention and control measures:

• destroying and burning plant debris, after harvest;
• chemical carrot treatments with specific fungicides.

White mold (Sclerotinia sclerotiorum)

The disease is commonly found in root crops, with the greatest damage reported in warehouses. If storage is done improperly, losses can reach 25%. The attack starts in the field, the basal part of the plant is covered with a white puff. If weather conditions are optimal (warm and humid), the plants can be destroyed. In storage, a white-brownish mycelium develops on the injured carrot roots. On this mycelium develops the fungus fructifications, represented by sclerotia. In storage, the disease is transmitted by direct contact.

Prevention and control measures:

• correct crop rotation;
• storage in optimal conditions;
• growing resistant carrot varieties;
• chemical carrot treatments with specific fungicides.

White tip of leek (Phytophthora porri)

The disease manifests itself on the roots in the form of black-brown moist strips. The affected tissue becomes rubbery or soft. Signs of infection may sometimes appear in the field, but in most cases, symptoms are visible immediately after harvest. The disease continues to develop in storage at low temperatures. In damp conditions, a dense white mold develops. This disease is associated with poor soil drainage.

Prevention and control measures:

• balanced fertilization;
• rational irrigation;
• avoiding soils with excessive humidity;
• chemical treatments with specific fungicides.

Cercospora leaf blight (Cercospora carotae)

The fungus attacks many parts of the plant. The attack is first seen on young leaves. Small, irregular spots appear on the leaves. The spots develop and become surrounded by a light-colored halo. The leaves wither and dry out. Cercospora can easily be confused with a bacterial disease.

Prevention and control measures:

• crop rotation;
• growing resistant carrot varieties;
• avoiding sprinkler irrigation;
• gathering plant debris after harvest;
• weed control;
• chemical treatments with specific fungicides.

The main pests of carrots

Root-knot nematode (Meloidogyne hapla)

It develops 1-3 generations per year and overwinters as an egg in plant debris or soil. It is a polyphagous species which attacks over 350 different species of plants. The nematode settles in the main roots of the plant. The attack results in excessive branching of the main root. This phenomenon is considered a plant defense reaction. Thus, the roots deform and lose their commercial appearance.

Control methods:

• crop rotation;
• disinfecting soil with specific products.

Slug (Deroceras agreste)

It is a polyphagous species that attacks many vegetable plants, flowers, vines, etc. It causes great damage to vegetable crops. Adults and larvae gnaw on emerging plants and their underground organs, where they dig galleries. Following a strong attack, plant vigor is reduced, leaves dry out and roots rot.

Prevention and control methods:

• ensuring a proper crop technology;
• ensuring an optimal density;
• chemical treatments with specific products.

Striped bug (Graphosoma lineatum)

It is a univoltine species, overwintering as an adult in the forest vegetation, in orchards, or on plant debris on the soil surface. Larvae and adults attack plants, destroying flowering shoots, causing flower abortion, or preventing plant growth.

Prevention and control methods:

• balanced fertilization;
• weed destruction;
• chemical treatments with specific insecticides.

Dock bug (Coreus marginatus)

It has one generation per year and overwinters as an adult in the forest. It is a polyphagous species that attacks mainly dill, carrots, parsnips, etc. It can attack all plant organs. In case of a severe attack, it causes seed drying, leaves drying, and prevents plant growth.

Prevention and control methods:

• balanced fertilization;
• weed control;
• chemical treatments with specific insecticides.

Aphids

They are polyphagous species that migrate from one plant to another or from one species to another. They grow on spontaneous flora and then move on to cultivated species. Aphids occur as a colony on the underside of leaves, flowers, or inflorescences and young shoots. Insects sting and suck the sap, causing stress to the plant. In case of a severe attack, it causes the death of the plant.

Control methods:

• using sticky traps;
• specific insecticide treatments.

Carrot weevil (Liparus coronatus)

It develops one generation per year and overwinters as mature larvae in the soil. Adults lay their eggs on the roots. Larvae dig feeding galleries in carrot roots. Attacked tissues become necrotic and carrots lose their commercial appearance.

Prevention and control methods:

• crop rotation;
• deep plowing;
• removing attacked plants from the crop;
• chemical treatments with specific insecticides.

Silver carrot conch (Aethes williana)

It develops one generation a year and overwinters as a mature larva in the soil, in carrot roots, or various sheltered places. The larvae burrow into the stems and dig galleries in the root zone, then enter the roots. In the wounds caused by the larvae, pathogens settle and cause root rot.

Prevention and control methods:

• proper crop technology;
• removing spontaneous umbellifers from the crop and the surrounding area;
• specific insecticide treatments.

Phytoecia icterica

It has one generation per year and overwinters as a larva in the roots of carrots, parsnips, etc. Females lay eggs in the ground near the roots. After hatching, the larvae enter the roots, where they dig galleries in the central cylinder. The roots rot as a result of the attack. In case of severe attacks, yield can be significantly reduced.

Prevention and control methods:

• gathering and destroying plant debris after harvest;
• correct crop rotation;
• treatments with specific insecticides.

Carrot fly (Chamaepsila rosae)

It has two generations per year and overwinters as a pupa in the plant debris from the soil surface. Females lay eggs in the ground near the plants. After hatching, the larvae enter the roots, where they dig galleries. Attacked plants die or develop small, inedible roots. Microorganisms can settle in the wounds produced by the larvae, leading to tissue rot.

Prevention and control methods:

• destroying plant debris, after harvest;
• removing attacked plants from the crop;
• treatments during vegetation with specific insecticides.