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Occurrence Characteristics and Comprehensive Prevention and Cure of Pumpkin Powdery Mildew
1. Incidence conditions The pathogen of melon powdery mildew belongs to Ascomycetes, Erysiphe spp., Erysiphe spp. or monofilament genus. Pathogens use mycelia or ascus to overwinter on sick bodies to produce spores, spread by wind and rain. Spore germination directly invades the epidermal cells of the host and draws nutrients from the host cells. The germination temperature of spores is 10-30°C and the optimum temperature is 20--25°C. The requirement for humidity is not strict and high humidity is conducive to germination. 2. Occurrence characteristics and prevention and control of powdery mildew in pumpkin farming 2.1 Wide spread and fast speed. Because powdery mildew is spread by wind and rain, there is no disease-free zone, which almost harms all melons, especially pumpkins, melons, zucchini, and other large-leaf melons. Cucumbers and melons are the second most serious infections. Weeds, poplars, sunflowers and other plants on the ground. Take Jiuquan for example, north to the edge of the desert and south to Qilian Mountain, all the melon seed production areas are infected with powdery mildew. It is characterized by many diseases and residues in the old planting area, with early infection, rapid spread and wide spread; the origin of the new seed production area is mainly spore transmission by rain and rain, slow development in the early stage, long incubation period, and easy to cause large outbursts with the accumulation of spores. , aggressive, heavy damage, difficult to control. 2.2 The occurrence of powdery mildew is not subject to special conditions. Powdery mildew originated from late May to early June. The temperature is appropriate during this period. Dew is present in the morning and humidity is high in the field, which is conducive to the occurrence of powdery mildew. After entering late June, with the rising of temperature, powdery mildew is in the incubation period. In the middle and late July, powdery mildew rapidly expands and spreads, all fields are infected, and prevention and control are not timely. In late July, there will be the fall of all fields. 2.3 The operation process and technical requirements promote the occurrence of diseases. The pollination period of pumpkin seed production is from mid-June to early July, and it belongs to the natural latent period of powdery mildew and the early stage of development. The method of artificial pollination is adopted in the production of pumpkins. Artificial propagation of powdery mildew is promoted artificially, and after pumpkin pollination is finished Requests for topping and snoring to ensure fruit's need for nutrients. As topping and squatting damage the growth point, new shoots and lateral branches cannot grow, photosynthesis is weakened, disease resistance in the middle and late stages of plant growth is reduced, and the incidence rate is significantly increased. If not controlled, the plant quickly withers, the fruit can not mature, the seed coloring is poor. The grain is not full and the yield is low. 2.4 The prevention and control techniques are not suitable and cannot control the spread of the disease in a timely and effective manner. One is improper prevention and control measures. In the production, it fails to formulate a complete set of prevention and control measures based on the occurrence rule of powdery mildew, but only when the occurrence of severe powdery mildew occurs, the prevention and control delays the timing, resulting in the rapid spread of the disease and can not be controlled. Second, improper use of pharmaceuticals, farmers generally use triadimefon, sulfur, chlorothalonil, thiophanate-methyl, lime, plant ash as a control agent, from the type of agent, there are certain control effects, but the use of various types of drugs, Application methods and control effects are different. 3. Control measures Pumpkin powdery mildew is prevalent and spreads widely. It is easy to produce drug resistance. The use of a single prevention and control method and a single chemical control effect are not ideal. Therefore, the prevention and treatment of pumpkin powdery mildew should be based on prevention, and it is not conducive to white powder. The occurrence of disease and conditions conducive to the growth and development of pumpkins can be achieved by early prevention, early detection and early control. 3.1 Strictly implement the isolation requirements in the technical specifications for hybrid seed production. The pumpkin's technical requirements for hybridization require not to select the most important plot. The isolation zone requires 2 km between the pumpkin and the pumpkin and 400 m between the pumpkin and the watermelon. These requirements are all aimed at preventing disease. 3.2 Appropriate early sowing to reduce the hazard of powdery mildew. The characteristics of powdery mildew occurring in mid-June in mid-July and spreading in late-July, and weather conditions and technical measures are allowed to be sown early in time to strive for fruit ripening before the occurrence of powdery mildew so as to mitigate the hazards. The combination of different varieties, the parents of different sowing time, from the Hexi area, the seeding period of the father to April 15- April 25 is appropriate, the mother of April 25-May 1 sowing is appropriate. 3.3 Early removal of cotyledons and basal leaves delayed the onset of disease. After many years of observation, I discovered that powdery mildew first occurred in the cotyledons and the first and second true leaves. In early June, the combination of whole vines and early clearance of cotyledons and the first and second true leaves can reduce the source of disease, delay the onset of disease, and benefit the fruits. mature. 3.4 Reasonable irrigation and fertilization, improve disease resistance. The large pumpkin leaves have a high degree of shadowing in the field and are susceptible to disease. The seeding water must be thoroughly irrigated, the water should be controlled early, and water should be poured before the pollination to control the growth of the pumpkin in the early stage so as to increase the disease resistance. In the use of fertilizers, emphasis on re-application of basal fertilizer, per acre applied maturity of farmyard fertilizer, 4 kg, multiple compound fertilizer 25 kg, timely fertilizer after pollination, mainly NPK combined fertilizer. 3.5 When the pollination is over, the plants do not pick up their hearts and enhance their viability. The hybrid seed production of pumpkin generally requires that the pollination of the plant after the end of pollination, multiple removal of lateral branches, buds, so that the plant lost its growing point, with the powdery mildew infection, the leaves can not be photosynthesis, nutrients can not be accumulated, the leaves quickly aging, plant With premature aging, the seeds cannot mature normally. Retaining the main vine growth point or lateral branch can increase the ability to produce new leaves, enhance plant vigor, delay plant senescence, and suppress the hazard of powdery mildew. 3.6 Removal of fallen leaves and leaves, reducing the number of pathogenic fruits, timely removing the debris from the field after the harvest, and reducing the accumulation of pathogens in the coming year. 3.7 Chemical control. At present, the control of powdery mildew is not yet ideal. Generally, triadimefon, carbazole, sulphur, lime sulfur, thiophanate-methyl, chlorothalonil, etc. are commonly used, and lime and ash are used individually. According to my comparison in production and application from 2000 to 2002, the control effects of various types of pesticides on powdery mildew were: lime sulfur> diniconazole> triadimefon> sulfur. The use of lime sulfur to control powdery mildew, pumpkin dumplings 15-30 days later than other agents; diniconazole late 8-20 days. Using plant ash, due to its strong alkalinity, the leaves of the pumpkin are prone to dehydration and dryness, which is caused by the fall of 3-5 days after application. Therefore, according to different periods, using different methods, the use of different agents for the prevention and control of powdery mildew is very important. After many years of practice, the author can classify the agents that control powdery mildew into three categories: The first category. Prophylactic agents, including lime and plant ash, can be used for their strong alkalinity and are used on the sides of the mantle or around the plant to prevent the intrusion of the disease. The second category. Early control agents include diniconazole, triadimefon, sulfur, thiophanate-methyl, chlorothalonil, and the like. Generally in early June, after the completion of the pruning, 70% thiophanate-methyl 1500--2000 dilution and 45% diniconazole 1000--1500 dilution were used. The third category. The agents used for the prevention and control of the later period are mainly lime sulfur, which has the effect of bactericidal and insecticidal. The early use is likely to cause phytotoxicity. After being used for pollination, the concentration requirement is 0.2--0.3 Baume, and it is sprayed three times until August. Medication is no longer used in the middle of the day.