First, Sclerotinia sclerotiorum commonly known as white rod, empty rod, hemp rod, rotten rod, mildew, etc. A disease caused by an Ascomycete strain. It occurs throughout the country. According to the degree of occurrence, it can be divided into: the severe ward of the middle and lower reaches of the Yangtze River and the southeastern coastal areas; the severe ward in the middle reaches of the Yangtze River; the mild ward in the upper reaches of the Yangtze River; the mild ward in the Yunnan-Guizhou plateau; the mild ward in the South China Sea; the light ward in the North China Sea; Ward and other seven wards. In addition to harming rapeseeds, they also infested such crops as Cruciferae, Asteraceae, Leguminosae, Umbelliferae, Malvaceae and Solanaceae. 1) Occurrence of rapeseeds After harvesting, the bacterium nucleus forms in the soil or mixed with seeds and fertilizers to overwinter overwintering. During the October-December average temperature of 5-18°C, part of the sclerotia in the soil germinates and infects rape. Constitutes the onset of disease. After the average temperature in the spring of the second year exceeds 5°C, a large number of sclerotia in the soil are generated to produce the ascidian plate. During the 2-4 month average temperature of 8-14°C, a large number of apical discs will appear; a large number of spores will be ejected within 8-15 days. Ascospores are transmitted by airflow, and ascospores germinate and invade the petals of rapeseed. The infected petals fall on the leaves and cause disease. Leaf lesions spread and spread to stem stems. The mycelium that spreads on stems spreads through the branches and leaves to adjacent healthy plants. Become the main route of disease transmission. The optimum temperature for sclerotial germination and the formation of the ascitium disk was 15°C, and the optimum temperature for ascospores invading the host and mycelial growth was 20°C. Overcast and rainy, the relative humidity above 80% is conducive to the growth and spread of germs. Partial application of nitrogen fertilizer, low-lying, poor drainage or plant density, are conducive to disease, mustard, Gan Lan rape and cabbage-type disease resistance. 2) Symptoms and Diagnosis Sclerotinia sclerotiorum is endemic to all parts of the rapeseed at all stages of development. The lesions at the seedling stage mostly occurred at the junction of the ground rhizomes, forming reddish-brown spots, which turned to dry and white afterwards. The tissues were wet and white white flocculent mycelium grew. After the diseased spot passes around the stem, stem rot occurs, seedlings die, and many black sclerotia form outside the diseased tissue. In the adult stage, the leaves are onset. They appear as round or irregular water-stained lesions at the beginning. The center of the lesion is gray-brown or yellow-brown. The edges are dark-cyan, slightly camouflage, the edges of the lesions are green, and the outer edges are yellow. The lesions were broken and perforated when dry, and rapidly expanded in wet conditions. The whole leaf rotted and white mycelium grew above. Stem disease, spindle-shaped light brown water-stained lesions appear first, slightly depressed, the central white, with a brown ring pattern. The lesion progressed very quickly under moist conditions and white mycelium grew above. In the late stage of disease, the epidermis of the stem was damaged, the filaments of the vascular bundle were exposed, the pith was hollow, and it was easy to fall down. Many black murine sac-like nucleus were formed in the stem. In severe cases, the whole plant withered, and the mildly diseased plants partially withered or matured earlier and the seeds were not full. After the petals became yellow, they turned white. After the pods are infected, irregular white spots are formed, and small and round seedling nucleus can be formed inside and outside the pods. After the seeds became infected, the surface was rough, grayish, dull or irregular.
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