In the cultivation of tomatoes in greenhouses in Linxiang District, continuous cropping of the same crops exists, which causes the cross-infection of Rhizoctonia solani, resulting in an ever-increasing area of â€‹â€‹tomato blight, and should be highly valued by vegetable farmers.
First, the symptoms of identification: seedling stage can be disease. The stems of the diseased seedlings turn brown, and the diseased part of the diseased seedlings shrinks. The stems and leaves are wilted and wilted; the large seedlings are wilted during the day and recover at night. When the diseased spot circles the stems one week, the seedlings gradually wither and usually do not fall down. The obscure dark brown spot of the diseased part, with concentric ring pattern and light brown spider silk mold, is an important feature distinguishing this disease from damping-off disease.
Second, the pathogen: The disease caused by Rhizoctonia solani, the pathogen belongs to the semi-mycotic fungus. The spores do not produce spores and are mainly transmitted and propagated by mycelium. The primary mycelium is colorless and tan-brown, and the branches are curled up at the base. The old mycelium often presents a series of barrel-shaped cells. Sclerotia are subglobose or amorphous, colorless or light brown to dark brown, and the spores are nearly round.
Third, the law of occurrence: The mycelium nucleus in the soil in winter, and rot in the soil 2-3 years. Mycelium can directly invade the host, spread through water and agricultural implements. Germ development temperature 24 Â°C, the highest 42 Â°C, the lowest 13 Â°C, suitable for pH3-9.5. Sowing too dense, timely seedlings, lack of light, the temperature is easy to induce the disease. In addition to harming tomatoes, germs can also infect eggplant, pepper, cucumber, beans, cabbage, rapeseed, and cabbage.
Fourth, control methods: (a) to strengthen the seedbed management, pay attention to improve the ground temperature, scientific ventilation, to prevent the emergence of seedlings or nursery tray high temperature, high temperature conditions. (B) Spraying 01%-0.2% dihydrogen phosphate planting 7500-9000 times liquid at the seedling stage to enhance plant resistance to disease. (C) Use seed weight 0.2% -0.3% of 40% seed dressing double, 50% carbendazim seed dressing. (D) Seedlings or seedlings disc soil treatment. 40% seed dressing double powder, 50% carbendazim wettable powder, 40% pentachloronitrobenzene and thiram 4:1 mixture can be used to treat the soil with 8g per square meter seedbed. First, add 5kg of fine soil and mix well, spread the bottom 1/3 and cover 2/3 (the method is the same as that of rape seedlings). Seedling blight alone area, single-use quintozene control effect is not high, can be mixed with the same amount of thiram or seed dressing double. In addition, the chloropicrin coating method can also be used, that is, applying 2-4 ml of chloropicrin deep at 10-15 cm every 30 centimeters after trimming, applying side cover soil. After all the applications were completed, they were covered with plastic film for 1 week, and then sowed or planted after 12-15 days of ventilation. (5) In the early stage of onset, spray 20% methyl-rhodium phosphorus (Licoc) 1200 times, or 36% thiophanate-methyl suspension 500 times, or 5% Jinggangmycin 1500 times, or 15%?f moldy spirit agent 40 times. When damping-off and blight mixing occur, 72.2% Precloxone 800 times solution plus 50% thiram WP can be sprayed with 800 times, 2-3L per meter, depending on the condition 7-10d, continuous Prevention and treatment 2-3 times.
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