Identify and occur:
The germs are mainly scattered in the soil or mixed with seeds, fertilizers, summer and winter, and in March and April, the climate is warm and humid, the sclerotia germinate in large numbers, resulting in ascidian disks, releasing a large number of germs (ascospores) and spreading with the wind. , against rape. Infestation of the base of the petiole in early stages of the plant and damage of the petiole, usually occurs first on the sides of the petioles near the ground or in the parts where the soil contacts. The lesions are yellowish-brown or dark brown, sometimes with inconspicuous ring veins, and with gray mold layer (mycelium In severe cases, it will cause the base rot. Afterwards, the pathogens may invade the leaves, stems and petals, but most of them fall from the petals and fall onto the leaves to cause the onset of the leaves. A round water-spotted lesion appears first and then becomes dark brown. Sometimes there are rings and a gray mold layer is produced on it. After the diseased leaves rot, they attach to the stems and cause stem diseases. The diseased stalk began to appear as a pale brownish watery spot and turned grayish. When the humidity is high, the diseased area is soft rot and the surface has white mold. After drying, the epidermis ruptures like a hemp, and the diseased stems are often easily blown by the wind. The branches and branches above the diseased part are withered and become yellow. The diseased stems are destroyed inside, rotted into hollows, and produce white mold and black murine fungi. nuclear. After the fruit has been damaged, it fades to whiteness, the seeds are thin, and there are fine sclerotia inside.
Incidence conditions:
(1) Bacterial source: The residual sclerotia of Lianchuang field is much, and the work of cultivating cultivator is not done well in time, which is conducive to the growth and reproduction of germs, which is a factor of the severity of morbidity;
(2) Cultivation and management: poor drainage, over dense planting, improper nitrogen fertilization, excessive rape growth, lodging, etc., poor ventilation and light in the field, high humidity, and also conducive to the propagation of germs;
(3) Temperature and Humidity: In the early spring of rape, it suffered from freezing injury, weakened disease resistance, and was easy to develop. In the suburbs of Shanghai, where temperatures are high in March and April, and when there are more rains, the incidence is often heavier. Especially in the period of rapeseed bloom, in case of high temperature and rainy weather, and with the cooperation of the above two conditions, there is a possibility that the disease may be in danger. .
Prevention:
Prevention and control of the disease should focus on agricultural control, and pay close attention to the control of flowering chemicals.
(1) Agricultural control: Breeding early-maturing, high-yield, and disease-resistant varieties, so that the main transmission period of the Xiehua period and the spores of the pathogens can be diverged as far as possible to achieve the purpose of disease prevention; it is a fundamental measure for preventing and controlling rapeseed sclerotinia; Do not stop the accumulation of water in the rain, in order to reduce the groundwater table and the field humidity; deep plowing deep, deep sclerotia; a planned rotation with wheat and crop rotation, to avoid continuous cropping; reasonable fertilization.
(2) Chemical control: The initial flowering to full flowering period uses 50% carbendazim WP for 1000 times, 25% gibberellin cleaning powder for 70 gram per acre, and 80 kg of water for spraying.