Control of three major diseases of carrot

Carrot (carrot), alias carrot, clove radish, gourd gold, also known as carrot, red vegetable head, yellow radish, etc., is an umbrella-shaped biennial herb with fleshy roots as vegetables to eat.

The three most common diseases of carrots are carrot black spot, carrot spot and carrot soft rot. These three major diseases have seriously affected the production efficiency of carrots, so what are the symptoms of the three major diseases of carrots, what are the causes, what are the conditions and how to control them? Let's introduce it next.

Carrot black spot

Carrot black spot is one of the major diseases in the country. Seed and plant disease, resulting in reduced yield and poor quality. Symptom recognition, petiole, stem disease. Leaves mostly from the leaf tip or leaf edge of the disease, resulting in small brown spots, there are yellow halos. After enlarged, it showed irregular dark brown, with light brown disease spot inside, covered with leaf margin and curled up, withered and yellow from the lower part. When wet, the disease spot on the dense black mold (conidia). Stem, pedicel disease, produce oblong dark brown slightly sunken disease spot, easy to break, the seed is not full, and with bacteria.

Cause: caused by Alternaria carrots. The pathogen overwinters on seeds and diseased bodies. The rate of carrying bacteria in seeds is high, which causes the seedlings to wither. The spores on the new spot in the second year are spread by airflow and invade directly from the stomata, wounds or epidermis.

The condition of the disease: the optimal temperature was about 28 ℃, and there was no disease below 15 ℃ or above 35 ℃. The disease occurred in the south in July and August. The disease is aggravated by lack of fertilizer and weak growth.

Prevention and control methods:

1. The seeds were mixed with 0.3% 50% prohydantoin wettable powder or 50% thiram wettable powder, 40% mixed with seeds and then sown.

2. Implement 2-year crop rotation.

3. Increase the application of base fertilizer and topdressing.

4. At the initial stage of the disease, spray 1500 times of 50% prohydantoin wettable powder, or 75% chlorothalonil wettable powder, 70% mancozeb wettable powder, once every 7 to 10 days, continuous prevention and treatment for 3 times.

Carrot spot disease

Carrot spot disease is a common disease on carrots, which is prevalent in high temperature period in summer and autumn. The disease of seed and plant affects the seed yield and quality.

Symptom recognition: disease on leaves, petioles and stems. Young leaves primary round or suborbicular 2-4 mm brown spot, enlarged in fusiform or polygonal, central grayish brown, margin slightly raised. When it is wet, there is gray mold on both sides. When it is severe, the disease spot connects into a piece, withering and dying from the lower leaves. Brown sunken disease spots were produced in petiole and stem. The disease is gray and old on the spot, which can be distinguished from black spot. In the field, it is often mixed with black spot.

The cause is caused by Cercospora carrots. The pathogen overwintered inside and outside the seed and on the diseased body on the surface. Spores are produced the following year and spread by wind and rain.

The condition of the disease occurred during the period of high temperature in summer. In the early stage, the plant was short of fertilizer and drought, and the plant growth was weak, and then the disease was serious due to rain, fog or poor drainage.

Prevention and control methods:

1. The seeds were mixed with 0.3% 50% prohydantoin wettable powder or 50% thiram wettable powder, 40% mixed with seeds and then sown.

2. Implement 2-year crop rotation.

3. Increase the application of base fertilizer and topdressing.

4. At the initial stage of the disease, spray 1500 times of 50% prohydantoin wettable powder, or 75% chlorothalonil wettable powder, 70% mancozeb wettable powder, once every 7 to 10 days, continuous prevention and treatment for 3 times.

Carrot soft rot

Carrot soft rot, also known as rot disease, is a common disease, which occurs frequently in the south. The disease of seed plant is serious.

Symptom identification: mainly harmful to fleshy roots. Chronic disease occurred in the field, with some leaves yellowing at first and then wilting. When the disease is acute, the whole plant suddenly wilts and wilts. Examination of the diseased plant showed that the root and stem softened in water, the flesh became grayish brown, softened and rotted, and the overflowing juice smelled.

The cause is caused by carrot soft rot Eucalyptus, which is the same as Chinese cabbage soft rot.

Disease conditions: germs invade from natural wounds, mechanical wounds, insect injuries and so on. Wounds are often caused by heavy rain after a long period of drought, storms, ploughing and loosening the soil, and pests on the ground and on the ground. The disease is serious in summer and autumn with high temperature, rainy days and poor drainage.

Prevention and control methods:

1. Rotation with field crops for 2 years, or rotation of flood and drought.

2. Direct seeding cultivation in high border should not be too dense, well ventilated and drainage should be strengthened.

3. Control pests on the ground and underground as soon as possible.

4. Watering should be controlled properly after the disease.

5. Diseased plants were found to be removed.

6. At the initial stage of the disease, 72% agricultural streptomycin sulfate can be sprayed 4000 times, or 14% complex ammonia copper solution, Fengling 200 times, once every 7 to 10 days, a total of 2 times.