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Pay attention to the prevention of watermelon seedling disease
Aphid root and seedling problems are two kinds of physiological diseases that are easy to appear in watermelon seedlings. After the roots of the melon seedlings occur, no new roots or adventitious roots will be made in the roots, and the root bark will rot after rusting, resulting in wilting in the ground and coking in the leaves. The ground temperature which is generally too low, plus excessive watering or rainy weather, the seedbed temperature is too low, it is prone to rooting; the stiff seedlings show a small amount of seedling growth, slow leaf development, grayish green leaves, cotyledons and true The leaves turn yellow and the roots turn yellow. In order to prevent and control physiological diseases, the melon farmers must control the breeding environment. First, bed soil for nursery should use new soil, fertilizer for preparing nutrient soil should be fully fermented and decomposed; second, the temperature of nursery should be controlled at 28°C～30°C. , At night not less than 18 °C; Third, seedbeds should be improved ventilation during the day, at night to do insulation. Especially in the low temperature and rain, when the light is insufficient, we must grasp the temperature to ensure that the temperature difference between day and night of nursery is between 5 °C ~ 8 °C; Fourth, the seedling water management should be based on seedbed humidity and weather, to prevent flooding. Non-physiological disease during seedling stage, damping off disease, blight and fruit spot disease occur relatively high risk. The roots and stems of watermelon seedlings are immersed in water-like lesions. Afterwards, the diseased part gradually turns brown and shrinks. The cotyledon is often not withered, and the phenomenon of seedlings suddenly falling to the ground is typical of damping-off. Blight frequently occurs when the bed temperature is high or in the late stage of nursery, which mainly damages the stem base or underground root of seedlings. In the early stage of disease, melon seedlings appeared oval dark brown lesions at the base of the stem, gradually sag inwards, and spread around the stems one week later, causing the stems to shrink and dry and the melon seedlings to die. Prevention and treatment of these two diseases should do a good job in the treatment of nursery beds and nutrient soils. Usually, every square meter of seedling bed is brewed with 40% carbendazim or 50% carbenicillin 15 to 20 grams of wettable powder. If diseased seedlings have been found in the seedbeds, they should be removed in time, and hay ash should be sprayed on the seedbeds to prevent the spread.