Powdery mildew is an important disease that affects strawberry production in greenhouses, with high frequency, strong fulminantness, and heavy damage. After the occurrence of powdery mildew in strawberry, generally 20% -30% reduction in production, weight up to 50%, and even no harvest, seriously affecting the yield and quality of strawberries.
First, the main symptoms of the greenhouse strawberry can be the entire growth period, the main violation of strawberry leaves, flowers and fruits. The leaf lesions were dark stains of varying sizes at the initial stage, followed by a white powder on the dorsal plaques. The lesions were red-brown at the late stage and the leaf margins were atrophic and scorching. After the flower buds are infected, the petals turn red and the buds cannot open. The young fruit can not normally expand after being infected, and wither and wilting; the result of the disease has a layer of white hair, the coloration is slowly uneven, the fruit loses its luster and hardens to stop growing, seriously affecting the commodity and food value of the strawberry. The whole plant died when severe.
Second, the occurrence of the characteristics of powdery mildew with mycelium or conidia in the soil and sickness on the winter, summer. Powdery mildew is an obligate parasite that mainly depends on diseased strawberry seedlings and other propagating materials for medium and long distance propagation. Air flow is conducive to spread of pathogenic spores in the field, spreading to strawberry leaves, flower organs and fruits. Strawberry powdery mildew is a low-temperature and high-humidity disease. The suitable temperature is 15°C-25°C. The suitable temperature for molecular spore formation and infection is about 20°C, and the relative humidity of air is above 90%. The ecological environment of strawberry in winter greenhouses is in line with the requirements for the occurrence and infection of powdery mildew. If we encounter continuous sunshine, rain, fog, snow, etc. in the late autumn to early spring (November to February), it is very beneficial to the occurrence and spread of the disease, causing frequent occurrence of molecular spores, repeated infections, and outbreaks. Disaster. Continuous cropping, failure to remove old leaves and diseased leaves in time, partial application of nitrogenous fertilizers, plant greening, improper planting, or improper ventilation and dehumidification are all likely to induce strawberry powdery mildew, and the incidence is heavy.
Third, prevention and control measures
Controlling the humidity in the greenhouse is an important means to control the disease. First, double row ridge transplanting and full-film covering technology should be adopted to increase the temperature of the ground, reduce the temperature difference with the shed, reduce the condensation and enhance the illumination. Followed by the establishment of drip irrigation or membrane watering facilities, if there is no membrane watering facilities, scientific water should be used, "Ninggan not wet" principle, so that small water ground irrigation, do not flood irrigation. Ventilation should be strengthened to reduce the humidity inside the greenhouse, and ventilation time should be extended as long as possible without affecting the growth of the strawberries. The ideal relative humidity in the shed is about 60% for flowering and setting fruit, and about 70% for fruit enlargement. In this way, not only is it beneficial to flowering results and fruit enlargement, but it can also significantly suppress the occurrence of diseases.
The key to chemical prevention is prevention. In the production of susceptible varieties such as Hongyan, Hongxia, etc., they are actively prevented twice with protective fungicides before flowering, with 2% Wuyimycin aqueous solution 200 times. Or 4% of agricultural anti-120 water agent 400 times, or 75% chlorothalonil WP 600 times spray, spray 7-14 days once, the effect of alternating use of better agents. After the onset of illness, use a protective and therapeutic agent to prevent and treat the disease. Disperse the granules with 50% Kresoxim-methyl for 3000 times, or 4% for the Tetraflumizole for 1000 times, or disperse with 10% difenoconazole. Granules 1500 times, or 25% pyraclostrobin EC 2000-3000 times, or 70% thiophanate-methyl 1000 times spray, spray 7-10 days, alternating use better. When the humidity in the greenhouse is high, the 50m 8m shed is shed with 4% 2% Ethericide or 20% chlorothalonil, or 99.5% with sulfur vapour. 20 grams of sulfur powder, fumigation 2 hours per day during the prevention period, the onset of fumigation every day for 8 hours, 7-10 times after continuous use to prevent the use of methods. The use of fumigants alternates better.
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