Chrysanthemum powdery mildew is one of the common diseases in flowers and it is distributed in both southern and northern China. Chrysanthemum powdery mildew causes poor plant growth, leaves dead or even does not bloom, seriously affect the effect of afforestation and flower production; the disease also harms cineraria, calendula, echinacea, gerbera, cosmos, aster, dali Chrysanthemum, zinnia, rose, rose, impatiens, beautiful cherry, okra, poinsettia, hollyhock, phlox, begonia, wisteria, etc. Symptoms of chrysanthemum powdery mildew at the beginning of the disease, yellow leaves with small white spots on the leaves, with the majority of positive leaves, the main damage leaves, petioles and young stems and leaves more susceptible to infection. When the temperature and humidity are appropriate, the lesions can rapidly expand and connect into a large area of ​​white powdery spots or gray moldy layers. In severe cases, the diseased leaves turn green and yellow; leaf and young shoots are curled, deformed, prematurely decayed and withered; stalks are bent, new shoots stop growing, flowers are small and small, plants are stunted sterile or do not bloom, and even die. phenomenon. Pathogens and the occurrence of powdery mildew caused by pathogenic fungi. In southern China, open field cultivation and northern greenhouses can be chronic diseases. The pathogenic bacteria live over the body of the diseased plant or in the soil. The temperature and humidity in the spring of the following year are suitable. The fruit of the ascites begins to crack and the ascospore is dispersed. The ascospores are spread by air currents and wind and rain, and can be invaded repeatedly. It can be affected from May to November, and frequently occurs from August to October. It is easy to infect at 20 to 25°C. Humidity, weak light, poor ventilation, and day and night temperature differences above 10°C are most likely to occur. Severe onset from September to October, mainly in the fall of the wet, dew, and fog in the humid environment of multiple infections. In the case of high air humidity, poor ventilation, and low light intensity, it is easily induced. When watering is excessive, the plants are too dense, or the effects of drought are impaired, and the cultivation and management are poor, resulting in weak plant growth. Control methods 1. Clear garden treatment: In the cultivation, attention should be paid to the removal of dense and yellow plant leaves, the removal of diseased plants, the removal of diseased leaves, and the concentrated burning or deep burial, which can greatly reduce the source of infectious pathogens. 2. Strengthen production management: Do not plant too dense, control soil moisture, increase ventilation and light transmission. To avoid excessive application of nitrogen fertilizer, phosphorus and potassium fertilizers should be applied to increase the disease resistance of plant leaves. When watering, leaves should be kept dry to prevent splashing of water droplets when watering and cause re-infection. 3. Drug control: potted soil or seedbed, soil medicine sterilization, 50% thiophanate-methyl and 50% thiram (1:1) mixture 600 to 700 times liquid spraying basin soil or seedbed, soil, up to sterilization effect. In the early stage of disease, 100% of the agricultural antibiotic 120 or antibacterial B0-10 emulsion may be sprayed, or 50% of Garrinone's wettable powder or 75% of threonine morpholine emulsion may be sprayed 1000 times every 10 days for 3 times. Disease control and spread can be controlled. Especially with 25% of the enemy off (propiconazole) EC 20 ml of water plus 100 kg of spray, spray 10 to 15 days 1 time, and even spray 2 to 3 times, the control effect is better. In addition, 70% of thiophanate-methyl WP can be used during the onset of disease, or 45 to 67.5 grams of 50% thiophanate-methyl WP, add 70 kg of water, and spray evenly, every 7 to 10 Spray 1 day, spray 2 to 3 times; also use 15% Tricine cream 1500 times, or 70% thiophanate-methyl wettable powder 800 to 1000 times, 50% polysulfide suspension 300 times, or 20 % Triadimefon EC 2000 times or 75% chlorothalonil wettable powder 600 times, 50% Trichoderma 1000 times, spray once every 7 to 10 days, even spray 3 to 4 times, can play a good control effect .
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