Occurrence and control of chrysanthemum powdery mildew

Powdery mildew of chrysanthemum is one of the common diseases in flowers, which is distributed in the south and north of China. Powdery mildew of chrysanthemum causes poor plant growth, withered leaves and even does not blossom, seriously affecting the effect of greening and beautification and flower production; it is also harmful to melon and leaf chrysanthemum, calendula, echinacea, African chrysanthemum, Persian chrysanthemum, emerald chrysanthemum, dahlia, zinnia, rose, rose, impatiens, cherry cherry, okra, poinsettia, hollyhock, fluke, begonia, wisteria and so on. Harmful symptoms of chrysanthemum powdery mildew in the early stage of infection, yellow transparent small white powder spots appeared on the leaves, mostly on the front of the leaves, mainly harmful leaves, petioles and young stems and leaves were more likely to be infected. When the temperature and humidity are appropriate, the disease spot can be expanded rapidly and connected into a large area of white powder spot, or gray powder mold layer. In severe cases, the diseased leaves faded and yellowed; the leaves and shoots curled, deformed, premature senescence and withered; the stem bent, the new shoots stopped growing, the flowers were few and small, the plants were dwarfed, sterile or uncivilized, and even died. The pathogen and occurrence regularity of powdery mildew are powdery mildew fungi, inulinosporium, and the sexual segment is two-spore powdery mildew. The disease can occur all the year round in open field cultivation in the south and greenhouse in the north of China. The pathogen overwintered in the stump of the diseased plant or in the soil, and it was suitable for temperature and humidity in the following spring, the ascospores were cracked, ascospores were scattered, and spread and spread by airflow and wind and rain, and could be infected many times. The disease can occur from May to November, and frequently occurs from August to October. It is easy to infect the disease at 20 / 25 ℃. It is most likely to occur in high humidity, weak light, poor ventilation and temperature difference between day and night above 10 ℃. The disease was serious from September to October, mainly in the wet environment of rainy, dewy and foggy in autumn. When the air humidity is high, the ventilation is poor, and the light is insufficient, the occurrence is more serious when the plants are watered too much, the plants are too dense or under the influence of drought, and the cultivation management is poor, resulting in weak plant growth. Control methods 1. Clear garden treatment should pay attention to cutting off overdense and withered yellow leaves, pulling out diseased plants, cleaning up diseased and residual leaves, concentrated burning or deep burial, which can greatly reduce the source of pathogen infection. 2. Strengthen production management and planting should not be too dense, control soil moisture, increase ventilation and light transmission. To avoid excessive application of nitrogen fertilizer, we should apply more phosphorus and potassium fertilizer to enhance the disease resistance of plant leaves. Attention should be paid to keeping the leaves dry during watering to prevent water droplets from splashing and spreading, or high temperature and humidity, invading the host and causing re-infection. 3, drug control basin soil or seedbed, soil drug sterilization, you can use 50% thiophanate methyl and 50% thiophanate (1:1) mixture 600mur700 times liquid spray basin soil or seedbed, soil, can achieve germicidal effect. At the initial stage of the disease, the disease can be sprayed with 100x emulsion of agricultural antibiotic 120 or antibacterial B0Mel 10, or 1000 times of Ruinong wet powder or 75% thirteen morpholine emulsion, sprayed once every 10 days, and sprayed 3 times continuously to control the occurrence and spread of the disease. In particular, with 25% enemy power to remove (propiconazole) EC 20ml plus 100 kg of water spray, spray once every 15 days, continuous spray 2 Mel 3 times, the prevention and control effect is better. In addition, during the onset period, 70% methyl thiophanate wettable powder 32m 48g, or 50% methyl thiophanate wettable powder 45m 67.5g, add water 70kg, stir and spray, spray once every 7Mel 10 days, spray 2Mel 3 times in a row You can also use 1500 times of 15% trimethoprim emulsion, 800Mel 1000x solution of 70% methyl topiramate wettable powder, 300x solution of 50% polysulfide suspension, or 2000 times of 20% chlorothalonil EC or 1000 times of 75% chlorothalonil wettable powder, spraying once every 7 times every 10 days for 4 times in a row.