Scientific prevention and control of sunflower sclerotinia

Sunflower sclerotinia, also known as white rot disease, is commonly known as rotten dish disease. This disease occurs in different degrees in the main sunflower producing areas every year. The incidence rate is generally about 50%, and when serious, it can reach 80% or more. It has a great influence on the yield and quality of sunflowers.
First, the symptoms Symptoms of sunflower sclerotia can occur during the entire growth period of sunflower, and the following two types of disease symptoms exist.
1. Standing dry type. From the beginning of the seedlings to the formation of the disk can occur. The disease at the seedling stage is mainly at the base of the stem, forming a water-soaked lesion around the stem. When it is wet, white flocculent mycelium grows. After drying, the diseased part shrinks and shrinks, black sclerotia are formed in the stem, and the plants are erect and withered to death. In the adult stage, the stem base is also dominant, showing a pale brown moist lesion, and then gradually expanding to the stem of the whole plant. The latter lesion is gray and white, the edge is brown, and the epidermis is broken. The destruction of the organization affected the transport of nutrients. The leaves began to turn yellow from the bottom up, withered and fell off, and finally the entire plant died.
2. Rotten disk type. This illness is mainly heaviest after the flowering period. When the disk is victimized, a water-soaked lesion appears on the back, and the receptacle turns brown and softens. In the rainy weather, the lesions began to expand rapidly and penetrated the disk. From the back of the black heart to the front, a white mycelium grew, causing the disk to decay and the grain to mature. In severe cases, the seed kernels were rotten or the seeds were rotten. Fall off.
Second, the cause of the disease is mainly caused by sclerotial germination. The sclerotia are wintered in the soil, diseased tissues and seeds, and they can generally live for 2 to 5 years in soil. There are two infections: one is the generation of a mycelium after sclerotia germination, and it directly invades when it comes into contact with the "host". This is the infection type at the seedling stage and the adult stage; the second is the sclerotia. Can produce the sub-capsule disk, ascospores spores spread to the "host" through the rain or insects, sunflower rot disc is caused by the infection of ascites. In general, when the temperature is at 20°C and the relative humidity is 80%, it is most suitable for the germination of sclerotia, and it is also the most serious period of flower disk disease. Especially in the rainy years, the incidence was highest in some low-lying drainage areas, poor ventilation and light transmission, and repeated land reclamation or ploughing. From July to August, the incidence is also highest when there is a lot of rain and low temperatures.
Third, prevention and control measures
1. Remove the diseased plant. When this diseased plant is found, it must be immediately removed and destroyed to prevent its spread.
2. Chemical control. (1) Apply 800-1000 dilutions of 40% lucid to spray the lower part of the plant and the back of the disk one or two times before or after the sunflower flowering; (2) Use 50% thiophanate-methyl wettability 1000 times liquid powder, spraying 1 or 2 times before or after sunflower blooming; (3) 50% fast-king 500-1000 times spraying at the seedling stage or flowering stage, the control effect can reach 80 % or more; (4) According to the law of the occurrence of Sclerotinia sclerotiorum, when the temperature reaches 18°C ​​to 20°C, the moisture content in the 0cm to 5cm deep topsoil is above 11%, and when the ascariat begins to unearth, it is the most likely substance to be spread on the ground. In good times, 70% of pentachloronitrobenzene can be used per hectare and 30 kg to 45 kg of chlorobenzene, 150 to 225 kg of moist fine soil, mixed in the sunflower field after mixing, can inhibit the germination of sclerotia and kill just germination. The young germ tubes have a bacteriostasis rate of 91.3%, and the control effect is 78.5%.

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