What are the symptoms of Sclerotinia sclerotiorum? How to prevent it scientifically and efficiently?

The incidence of Sclerotinia sclerotiorum can be seen in the middle and late March of each year, and the temperature is 5 ~ 20 degrees. First, the lesion appears on the lower leaves. The leaf spots are round or irregular, and the color is yellowish brown or grayish white. Typical spots are multi-layer concentric wheel patterns, and the back of spots is livid. White cotton can be seen in bottles with high humidity in the field. The diseased disc of the stem is spindle-shaped or long-rod-shaped, with light brown scales, and then gradually turns gray. When the humidity is high, the diseased disc is soft, with a layer of white cotton fungus on the surface and hollow inside, and the epidermis breaks after the stem is dry in the later stage. I saw diseased petals, greasy brown spots, and the incident angle was similar to that of the stem point. The Ministry of War is grayish white with rough skin. Some Labiatae are surrounded by white hyphae, forming sclerotia.

If the rape suffers from rainy weather from the early flowering stage to the mature stage, the field humidity is the biggest factor affecting the incidence of Sclerotinia sclerotiorum. At the flowering stage of rape, the disease is serious when the rainfall exceeds 50 mm in 10 day and the relative humidity exceeds 85%. In addition, if rape is continuously planted or cruciferous vegetables are replaced, it is also easy to get sick. In addition, if immature rape straw is used as fertilizer, the amount of seeds is large, rape seedlings are too dense, nitrogen fertilizer is too much, the terrain is low, the field drainage is poor, and Sclerotinia sclerotiorum will occur in early spring and late spring.

Sclerotinia sclerotiorum is mainly Sclerotinia sclerotiorum, which is parasitic on soil and diseased body and overwinters. Seeds can also bring bacteria. In February of that year, 10 ~ 12, a few buds invaded the bud body. In February-April of the following year, under appropriate conditions, the sclerotia of the soil will produce ascomycetes, release ascospores and spread with the airflow. Invasion of wounds, petals, etc. The temperature is 20 degrees Celsius and the relative humidity is above 85%, which is beneficial to infiltration. The flowering period is very serious, just like rainy weather. Low terrain, poor drainage, too dense planting, poor ventilation of Dojo plots distributing nitrogen fertilizer, and continuous cropping plots are sick.

Reasonable rotation, and rice rotation must be more than 2 years. Seed treatment, removing sclerotia with 20% ammonium sulfate water. Timely sowing, rational fertilization, and timely elimination of field ills. When the leaf disease rate is below 10% and the stem disease rate is below 1%, drug control can be started. The available chemicals are: 1000 times of 40% Junjing wettable powder, 1000 times of nongliling, 1000 times of mycophenolate mofetil, 1200 times of thiamine, thiamine, encyclopedia (bis-triazole), chlordane, etc.