Affected by the high-temperature and humid micro-climate of facilities cultivation, strawberry powdery mildew has become more and more serious in greenhouses, generally causing 10-25% of production losses and 30-50% of serious production losses. At present, high incidence of strawberry powdery mildew in greenhouses should be strictly controlled.
Greenhouse strawberries can develop throughout the growing season, mainly affecting strawberry leaves, flowers and fruits. After the leaves became sick, a thin frost-like powder appeared on the leaves at the initial stage. When the conditions were appropriate, it quickly spread to the whole plant. As the condition aggravated, the leaf margins rolled upwards, and dark stains and white powders of different sizes appeared on the leaves. The material was reddish-brown at the late stage and the leaf margin was atrophic and scorch. After the flower buds are infected, the petals turn red and the buds cannot open. The young fruit is susceptible to disease and the fruit does not expand normally. After the fruit enlargement, the fruit surface is covered with a layer of white powder, which loses its luster and hardens and loses its commercial value.
The powdery mildews were overwintering and overwintering in the soil and the diseased bodies with mycelia or conidia. 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. The optimum temperature for pathogenic infection is 15-25°C, and no disease occurs when it is lower than 5°C or higher than 35°C, but wet and rainy weather will aggravate the disease. It usually occurs from early February to early May and peaks from March to March.
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. Strawberry powdery mildew is easy to prevail at moderate temperature and high humidity. In case of rainy days, it turns to sunny days. The temperature in the greenhouse is suitable and the humidity is high. The rate of propagation of pathogens and the spread of disease are accelerated.
Prevent strawberry strawberry powdery mildew in the greenhouse, control spraying once in the early stage of disease, and prevent and treat 2-3 times of continuous crops with severe disease. Triadimefon, myclobutanil, and cegolide are commonly used agents for the control of powdery mildew in strawberry, with good efficacy. Triadimefon is easy to produce phytotoxicity during the fruiting period of strawberry flowering, and has low safety to bees. It is not suitable to be applied during flowering and fruiting period of strawberry. It can be applied at the seedling stage, and it is usually sprayed with 15% triadimefon 1000 times liquid. Myclobutanil and Sego had no adverse effects on the growth of strawberries, and had high safety to bees. They could be sprayed with 12.5% ​​of myclobutanil or 20% of Segovia 1500 times. Do not arbitrarily increase the application concentration. The use of high concentrations of triadimefon at the seedling stage will result in failure of the seedlings and slow growth of the seedlings; excessive application of myclobutanil at the flower and fruit stage will result in the formation of stale fruit. Flowering usually takes place after 4 pm. Note alternate medications to delay the development of drug resistance. The drug was stopped 7 days before harvest. In addition, timely removal of old leaves, diseased leaves and diseased fruits, and bring them out of the field for centralized destruction; greenhouses to maintain ventilation and light, at night to maximize the temperature of the shed, to avoid dew exposure; reasonable irrigation, control the humidity within the shed; reasonable fertilization to prevent Partial application of nitrogen fertilizer and other agricultural measures, to a certain extent, can also reduce the incidence of strawberry powdery mildew.
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