Mainly occurs in greenhouse and plastic greenhouse cultivation environment. In northeastern China, North China, East China provinces have occurred. This disease only occurs in tomatoes. (I) Pathogens and Infections This disease is an invasive disease, which is caused by the infection with a species of Cladosporium spp., and belongs to the subgenus Clostridium spp. in the classification of pathogens. After the bundled conidiophore stems stick out of the stomata of the organ, it turns brown later and gives birth to a conidium with a septum. Along with the growth and development of the pathogen, symptoms will appear on the leaves, stems, flowers, and fruits of the tomato. However, common symptoms occur on the leaves. In the initial stage, some green spots appear on the back of the leaves, and later become gray or dark purple irregular layer of mold. The front of the leaves retreats to yellow in the corresponding parts. In severe cases, the leaves often appear. Dry curling. From the order of onset, often from the lower part of the plant to spread upward, the overwintering body of the bacteria is a mycelium or mycelium block attached to the diseased tissue of the plant, and some conidia attached to the surface of the seed, or latent hyphae Winter in the seed coat. The pathogen that remains in the soil or seeds in the second year becomes the source of the initial infection. The mycelium grows and spreads to produce conidia, which is transmitted by air currents. The conidia on the seed surface and the mycelium remaining in the seed coat produce conidia after growth and development. This is also an initial infection of leaf mold. source. In short, regardless of whether it is in diseased tissues or inside or outside the seed, the production of conidiospores is used as a propagator, and repeated infections are repeated and repeated, causing significant loss in the field. Which conditions are conducive to infection? The main condition is temperature, and the pathogen can grow and develop from 9°C to 34°C. The optimum temperature for development is 20-25°C. At the optimum temperature and humidity (above 80% relative humidity), it takes only 10 days to half months for widespread disease. Coupled with poor ventilation and light, it is more conducive to promoting disease. In greenhouses and greenhouses, especially in autumn greenhouses, high humidity and poor light conditions are common. From summer heat to late autumn, Shandong is used as an example. In August and September and early October, it is the temperature for pathogenic fertility. Therefore, the autumn greenhouse is heavier than the greenhouse, and the greenhouse is heavier than the open land. Focus on environmental protection is the autumn greenhouse tomatoes. (II) Micro-pollution and Non-pollution Control Techniques 1. Pay attention to selecting the seeds of early-maturing varieties from the spring dew spot for seed selection and seed treatment. At the same time, the seeds were treated with 52°C for 30 minutes to remove pathogens inside and outside the species. After treatment, it is best to rinse with water several times to remove pathogens attached to the primary water and seed surface. 2. It is advisable to arrange the cultivation of tomato crops in the shed for crop rotation. It is best to arrange a three-year crop rotation plan with melons or other solanaceous vegetables to eliminate the residual bacteria in the soil. 3. Cultivation management and control are based on the application of phosphorus and potash fertilizer, and often pay attention to the ventilation of the greenhouse, increase the line spacing and increase the light area. The sorghum is cultivated to control the soil temperature, and the old leaves on the ground are promptly removed to remove the bacteria source and increase the ventilation and light transmission conditions. 4. High-temperature stuffy sheds were selected for sunny days at noon, and were treated with high temperature of 30-36°C for two hours or so, and then they were ventilated and cooled to provide positive control of pathogens. 5. Greenhouse disinfection In sheds that are difficult to change crops, the area per 1000 square feet before planting acres is ignited overnight with a dose of 0.25 kg of sulphur powder and then sterilized. After a cool day or more, cut the seedlings, or use a bacteriostatic aerosol, disinfect the space and topsoil at a dose of 0.25 kg per 1000 square feet of medicinal powder. Calculated from a practical point of view, generally 0.3-0.5 mu of plastic sheds, dosage of 0.5-1 kg can be used. 6. The spraying protection is 1:1:240 times more Bordeaux mixture. It is sprayed once every 10 days from the initial fruit stage. The effect is good and the pollution is very light. When spraying, pay attention to even spraying, the focus is on the back and ground. A similar effect can also be obtained with 75% chlorothalonil wettable powder 600-800 times or 50% carbendazim wettable powder 500-800 times.
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