1 Pathogens and Hazard Symptoms The bacteria are obligate parasites that can only be parasitic on living organisms. In addition to harming melons, it can also damage legumes and vegetables and a variety of herbs and ornamental plants. Powdery mildew mainly harms leaves and sometimes infects branches. A white powder is formed on the surface of the leaf surface, the leaf back and the twig, and a small yellow spot which gradually changes to a yellowish brown to dark brown color on the white powder layer, that is, a closed capsule of the pathogen, is formed on the white powder layer. The lesions on the leaves are not obvious, and they are yellow-white plaques. When they are severe, they are curled and burnt; the shoots are distorted after being infected, and finally die.
2 Incidence conditions The temperature of the disease in the greenhouse is 16 to 24 °C. It has a wide adaptability to humidity. When the air humidity is between 45% and 75%, the disease is rapid. When it exceeds 95%, it can significantly inhibit the development of the disease. It is generally mild in years when rainfall is low. The disease developed rapidly in the face of cloudy weather and hot weather. In the case of weak or long plants, it is also easy to develop.
3 The law of the disease The bacteria overwinter on the diseased leaves and diseased branches. In the second year, the pathogens spread through the wind and rain. The pathogen invades the leaves from the stomata, and a large number of white powdery pathogen spores are produced on the leaf back to spread the disease. When the conditions are appropriate, the disease occurrence cycle is very short, and the infection can be repeated multiple times in one year. After the onset of the disease, the condition is generally heavier. If the prevention is not timely, it is difficult to control. Therefore, it is necessary to cooperate with the prevention and treatment on the basis of prevention.
4 Comprehensive prevention and control 4.1 Strengthening cultivation management It is necessary to pay attention to cultivating strong seedlings, rationally close planting, timely pruning and threshing, improve ventilation and light transmission conditions, and make plants grow robust and improve disease resistance.
4.2 Cleaning of the sheds Timely clean up the diseased branches and diseased leaves, concentrate on stacking or burning, and do not throw them away to prevent the spores from flying in the shed.
4.3 Rational Fertilization The base fertilizer needs to be added with phosphorus and potassium fertilizers to avoid excessive use of nitrogen fertilizer during growth. Watering and topdressing at the right time to enhance plant growth potential and disease resistance.
4.4 Smoked technology In the early stage of powdery mildew, every 50 square meters of sulfur with 120g, sawdust 500g mix well, split a few, start fumigation for 1 night in the evening, open the shed in the morning on the second day, or use 45% chlorothalonil smoked The agent was fumigated at 3.75 kg per hectare.
4.5 Ecological control The shed scent should strengthen ventilation management and control the development and infection of pathogens. In the morning on a sunny day, wind protection is required, so that the temperature of the shed rises rapidly. The temperature of the shed rises to 33 °C and then the top wind is released. The high temperature above 31 °C can slow down the spore germination speed of the bacteria, delay the sporulation, and reduce the sporulation. When the temperature of the shed falls below 25 °C, the wind will continue to be kept at noon, so that the shed temperature will remain at 20-25 °C. When the shed temperature drops to 20 ° C, close the vents to slow down the night shed temperature, and keep the night shed temperature at 15 ~ 17 ° C. Turn on the vents on a cloudy day.
4.6 Chemical control The chemical control is carried out before or during the onset of the camphor. 40% Fuxing emulsifiable concentrate 8000 ~ 10000 times liquid or 30% Teflon WP 5000 times solution, 40% polysulfur suspension 600 times solution, 30% Baike emulsifiable concentrate 3000 times solution, 6% erbi colable WP 4000 times liquid, 2% agricultural anti-120, Wuyincin 200 times liquid, evenly sprayed on the branches and leaves. When spraying, pay attention to the middle and lower old leaves and the back of the leaves. In the early stage of the disease, spray once every 7 to 10 days for 2 to 3 times, which can achieve better control effect.
Powdery mildew is the main disease of camphor. In recent years, the disease has become more and more common. It has caused serious threat to the production of camphor, and the yield loss is as high as 70%. It is more common in the southern region. The rate of general diseased plants is 30% to 50%. In severe cases, the diseased leaves reach more than 50%, which seriously affects canopy development and tree potential, reduces the yield and quality of axillary buds, and chemical resistance is easy to produce resistance. Therefore, it is necessary to use scientific and rational use of chemical agents to reduce the harm of germs, mainly based on the principle of agricultural control and supplemented by chemical control.
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