Cucumber downy mildew is a devastating disease of cucumber and one of the most common diseases. Once onset, it generally reduces production by 15% or more, and serious by more than 50%. Comprehensive measures must be taken to prevent and control the disease. First, scientifically regulate greenhouse temperature and humidity. The occurrence and prevalence of downy mildew is closely related to the temperature and humidity in the greenhouse. When the temperature reached 15 °C ~ 24 °C, the relative humidity of the air reached 80%, suitable for disease. Above 28°C, relative humidity below 70%, and leaves without water-film or water droplets, it is unfavorable. Therefore, by adjusting the temperature and humidity, the incidence can be reduced. The specific approach is: After one hour of sunrise, the greenhouse will let off air for one hour, so that the air in the shed can convectively lower the temperature. The temperature rose to 28 °C ~ 32 °C, and then released. At noon to increase the air outlet vent, so that the temperature dropped to 20 °C ~ 25 °C, humidity dropped to 70% or less, before the wind once again before sunset, the upper part of the night temperature 15 °C ~ 20 °C, humidity 60% ~ 70%, the next night When the humidity increases, the temperature is lowered to 12°C to 13°C. In this way, the optimum temperature for spreading downy mildew and the optimum air humidity are relatively staggered, and the occurrence of diseases can be controlled. If carbon dioxide is applied and the vents are on, carbon dioxide is less than air, and in the case of slow convection, carbon dioxide rarely escapes outside the shed. In order to reduce the humidity, the ground shall be covered with plastic film, and it must be prevented from flooding with large water. Small furrow irrigation should be carried out. Second, high temperature stuffy shed. The spores of Pseudoperonospora cubensis often die at 42°C, while cucumbers can tolerate high temperatures of 45°C in a short period of time when there is sufficient water. Therefore, raising the temperature in the greenhouse to 45°C can effectively kill pathogens. When the shed is drenched, select sunny weather and pour the water on the previous day. The sapodilla was first loosely sagged and the thermometer was hung in the same height as the tip (the thermometer was used for proofreading). Close the greenhouse at noon, so that the temperature rose to 45 °C, and maintain 1.5 hours to 2 hours, observed once every 15 minutes, the maximum temperature must not exceed 48 °C, otherwise it will burn the leaves. If it is found that the top leaves of the melon shoots begin to wilt, they have reached the critical temperature of the burning, and should be gradually released. To consolidate the boring effect, it should be reburied four days later. Third, improve the plant's physiological resistance. 1, nurturing strong seedlings is the foundation of disease resistance. 2, foliar spray fertilizer: Before the onset of experience, in the early morning with sugar nitrogen solution (0.5 kg of sugar and urea plus fresh water 75 kg) spray the back of the leaves, spray once every 5 days, even spray 4 times, can be effective Prevent the occurrence of downy mildew. In addition, 0.2% potassium dihydrogen phosphate solution plus 1% urea solution, plus 0.2% borax solution for extra-root fertilizer, can also improve disease resistance and reduce the incidence. 3. Adding carbon dioxide gas fertilizer: After the seedlings exhibited 3 true leaves, they began to increase the carbon dioxide fertilizer concentration of 800PPM. When sitting on the melon, the concentration of 1000PPM to 1500PPM can increase the photosynthetic rate and increase the nutrients in the body. 4, timely removal of the bottom of the faded leaves, timely topping in the late, reducing nutrient consumption. Fourth, chemical control. Chemical control should adhere to the principle of prevention and treatment, alternating use of pesticides and other principles. When entering the flowering stage, when the average temperature in the shed is 15°C and the relative humidity is more than 80%, the key areas for prevention and treatment (from the three-quarters of the sheds in the southern half) and the first four to five days of the experience period should be controlled. . Commonly used pesticides include 25% of the 1000 times Syriza 1000 times, 75% of chlorothalonil 600 times, and 40% of 300% aluminum diethylphosphate. These pesticides can be mixed and used interchangeably. The spraying should be even and thoughtful, with the back of the sprayed leaves as the main, and it should be controlled once every 7 days to 10 days, and the condition can be controlled by spraying three times.
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