What are the prevention and control methods of Sclerotinia sclerotiorum in Chinese cabbage?

Cabbage is the main vegetable in winter and spring in Northeast and North China. Raw food, fried food, salt pickling, soy sauce can be; the outer layer of leaves can be used as feed. Chinese cabbage has a wide variety, rich nutrition, and has a certain medicinal value, which is widely planted in many places in our country. Chinese cabbage is easy to get Sclerotinia sclerotiorum, what are the prevention and treatment methods of the disease?

Symptoms of Sclerotinia sclerotiorum in Chinese cabbage

When the seedlings were injured at the seedling stage, the heart leaves of the seedlings showed bright veins and chlorosis along the veins, followed by mosaic and wrinkling. Irregular watery spots appeared at the base of the stem, gradually soft rot and white mildew, resulting in quenching.

When the adult plant is injured, the disease occurs from the base of the leaf side near the ground, and then extends to the whole leaf until the whole leaf bulb. waterlogged light brown disease spots are produced on the damaged leaves, which cause rot at the base of the leaf ball and stem under wet conditions, but there is no stench. There are white cotton floss mycelium and black sclerotia on the surface and root of the diseased part. Small brown spots can be produced on the petiole and turn bright yellow around the spots. In a dry environment, the disease is dry and perforated, with white mycelium and black sclerotia. With the development of the disease, the leaves withered until the whole plant died. If the disease occurs rapidly, the plant will wilt and die quickly, and finally the stem epidermis of the diseased plant will rot and peel off.

The stalk of the seed-collecting plant was diseased, the stalk was light brown and sunken at first, then turned white, the cortex was rotten, the fibers were scattered into hemp-like, the stem cavity was hollow, and the endophytic black mouse fecal sclerotia. If the disease occurs rapidly, the whole plant wilts and dies soon. The damaged plants often dry up and die before they blossom, resulting in no harvest. The disease of the remaining plants with disease during the storage period is particularly serious, which is a destructive disease.

Second, what are the prevention and control methods of Sclerotinia sclerotiorum in Chinese cabbage?

1. Eliminate sclerotia

Because the sclerotia is the primary infection source of the disease, so eliminating the sclerotia is the first measure to prevent the disease.

① rotation. The implementation of interannual rotation with rice or gramineous crops can cause a large number of sclerotia in the soil to die out.

② deep ploughing. After the cruciferous vegetables were harvested, a deep ploughing was carried out and the sclerotia was buried in the soil layer below 2-3 inches, so that the ascomycetes could not be produced or could not be pushed out of the soil surface. Deep ploughing is one of the important methods to reduce the source of disease in dry land. In addition, ploughing in the stage of ascus formation can destroy the production of ascomycetes or bury them in human soil and reduce the transmission of ascospores.

③ seed treatment. Seeds should be collected from disease-free and robust plants. If the seeds are mixed with sclerotia, the seeds can be selected with 10% salt water or 20% ammonium sulfate water to remove the sclerotia floating on the surface. The treated seeds must be washed repeatedly with clean water before sowing, so as not to affect the germination rate.

2. Remove the yellow leaves

The complete removal of the lower yellow leaves of the plant can not only prevent the pathogen from spreading through the senescent yellow leaves, but also improve ventilation and light transmission, reduce humidity, and inhibit the disease to a certain extent. Picking yellow leaves can be carried out once at the early flowering stage and at the end of the flowering stage. The removed yellow leaves should be concentrated and buried deeply.

3. Rational fertilization

Avoid partial application of nitrogen fertilizer, increase the application of phosphorus and potassium fertilizer, and improve plant disease resistance.

4. Prevent flood irrigation and timely drainage after rain. The low-lying land is cultivated in high border.

5. Strengthen the management of vegetable cellar

Before and after the plant cellar, you should strictly guard against freezing. When the temperature of the pit rises and the humidity is too high, it is necessary to ventilate and reduce the humidity in time, pour vegetables and remove diseased plants in time, and strictly prevent the spread of disease in the pit.

6. Chemical control

When seed collection plants enter the flowering stage, if the rate of diseased leaf plants reaches 10% and the rate of diseased stem plants is about 1%, they should start spraying, and then spray it once every 10 days or so for a total of 2-3 times. The solution should be sprayed on the base of the stem, old leaves and ground of the plant. The commonly used agents are 1000-fold solution of 70% methyl topiramate wettable powder, 1000-fold solution of 50% thiophanate wettable powder, 50% carbendazim wettable powder and 50% clonitramine wettable powder. 5% clonitramine powder 2-2.5 kg / mu mixed with fine mud powder 15 kg, or 70% pentachloronitrobenzene powder 250 g / mu mixed fine mud powder 15 kg, evenly sprinkled on the ground between rows.