Downy mildew is one of the most common and most important diseases in the process of cucumber cultivation. Many farmers' friends are familiar with it and fear it. They are familiar with basic identification. The fear is that it is difficult to control how to fight drugs after getting sick. . It is often the case that farmer households are willing to increase the dosage of pesticides, increase the frequency of mixed pesticides and the frequency of pesticide application. There are even cases where drugs are given once every two or three days, often not only failing to effectively control the disease, but often causing phytotoxicity, production cuts, and even destroying the shed. The result is miserable.
Why is downy mildew so hard to cure it? First, let everyone know about cucumber downy mildew.
Common symptoms of downy mildew: lesions are yellow-brown polygons along the veins, not easy to perforate; when the humidity is high, the back of the lesion produces gray moldy pathogens. In the absence of brucellosis, the main difference between downy mildew and angular spot disease is that the diseased leaves are carefully observed against the light, the leaves of the diseased spot are a bit transparent, and the downy mildew leaves are not transparent. The diseased spot of keratoses eventually breaks, but downy mildew does not.
Downy mildew conditions: slightly lower temperatures and higher humidity. The suitable temperature is 16°C~24°C, less than 10°C, and the downy mildew is not easy to occur above 28°C. The relative humidity of air is more than 85% and the incidence is easy. The humidity is lower than 70%, and the spores of the pathogenic bacteria are difficult to germinate and infect. As long as there is a water film on the cucumber leaf surface, if the temperature is appropriate, the downy mildew pathogen can infect once in 6 hours.
So, how to prevent and control cucumber downy mildew more effectively?
"Prevention-based, comprehensive prevention and control" is its most basic prevention and control strategy. While controlling the temperature and humidity in the shed, it can be combined with the prevention and treatment of pharmaceuticals:
1. On the basis that the temperature drop of the shed does not exceed 2°C, uncover the grasshopper as soon as possible, and let the Z-shaped air outlet blow off air for 10 to 20 minutes to release the exhaust gas from the shed.
2. In the morning, when the temperature in the shed reaches 30°C~35°C (above 35°C to consume nutrients), the first tuyere is ventilated, and the spray agent is used to spray the cream first (10% dimethomorph). + Scaling (copper ferric acid copper) treatment, 5 days after the frost mold epidemic net (72% cream urea. Manganese zinc) protection and treatment, spraying the middle and lower leaves and the back of the leaf.
3. After noon, adjusting the tuyere will gradually reduce the temperature to 20 °C ~ 25 °C, conducive to the growth and transportation of nutrients cucumber, when the humidity is basically 60% ~ 70%, leaves no water film, downy mildew does not occur.
4, before and after sunset, try to prolong the time of exhalation, can effectively reduce the night leaf spitting 50%; when the temperature closes the tuyere at 22 °C, dropped to 18 °C when the grass rafts, the first half of the night although the temperature suitable for downy mildew but leaves no The water film will not be affected. Although the leaves in the middle of the night have a water film, the temperature has dropped to about 12°C~15°C, which is not conducive to disease. And no effect on the growth of cucumber. In the evening, the smoke agent can be used for fumigation and the effect is better.
To sum up, prevention and control of downy mildew disease in the shed to do a good job of small-climate adjustment, cultivating robust plants, after the onset of drug prevention and control, downy mildew prevention is no longer difficult.
Why is downy mildew so hard to cure it? First, let everyone know about cucumber downy mildew.
Common symptoms of downy mildew: lesions are yellow-brown polygons along the veins, not easy to perforate; when the humidity is high, the back of the lesion produces gray moldy pathogens. In the absence of brucellosis, the main difference between downy mildew and angular spot disease is that the diseased leaves are carefully observed against the light, the leaves of the diseased spot are a bit transparent, and the downy mildew leaves are not transparent. The diseased spot of keratoses eventually breaks, but downy mildew does not.
Downy mildew conditions: slightly lower temperatures and higher humidity. The suitable temperature is 16°C~24°C, less than 10°C, and the downy mildew is not easy to occur above 28°C. The relative humidity of air is more than 85% and the incidence is easy. The humidity is lower than 70%, and the spores of the pathogenic bacteria are difficult to germinate and infect. As long as there is a water film on the cucumber leaf surface, if the temperature is appropriate, the downy mildew pathogen can infect once in 6 hours.
So, how to prevent and control cucumber downy mildew more effectively?
"Prevention-based, comprehensive prevention and control" is its most basic prevention and control strategy. While controlling the temperature and humidity in the shed, it can be combined with the prevention and treatment of pharmaceuticals:
1. On the basis that the temperature drop of the shed does not exceed 2°C, uncover the grasshopper as soon as possible, and let the Z-shaped air outlet blow off air for 10 to 20 minutes to release the exhaust gas from the shed.
2. In the morning, when the temperature in the shed reaches 30°C~35°C (above 35°C to consume nutrients), the first tuyere is ventilated, and the spray agent is used to spray the cream first (10% dimethomorph). + Scaling (copper ferric acid copper) treatment, 5 days after the frost mold epidemic net (72% cream urea. Manganese zinc) protection and treatment, spraying the middle and lower leaves and the back of the leaf.
3. After noon, adjusting the tuyere will gradually reduce the temperature to 20 °C ~ 25 °C, conducive to the growth and transportation of nutrients cucumber, when the humidity is basically 60% ~ 70%, leaves no water film, downy mildew does not occur.
4, before and after sunset, try to prolong the time of exhalation, can effectively reduce the night leaf spitting 50%; when the temperature closes the tuyere at 22 °C, dropped to 18 °C when the grass rafts, the first half of the night although the temperature suitable for downy mildew but leaves no The water film will not be affected. Although the leaves in the middle of the night have a water film, the temperature has dropped to about 12°C~15°C, which is not conducive to disease. And no effect on the growth of cucumber. In the evening, the smoke agent can be used for fumigation and the effect is better.
To sum up, prevention and control of downy mildew disease in the shed to do a good job of small-climate adjustment, cultivating robust plants, after the onset of drug prevention and control, downy mildew prevention is no longer difficult.
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