(A) symptoms The disease can occur in any part of the fruit, the initial lesion round, light brown, rapid expansion of the disease, rapid spread of the whole fruit, diseased brown water stains, become soft. In a high-temperature, high-humidity environment, the disease minister produces a soft white hyphae that clings to the fruit surface to form a thin layer. The diseased fruit produces a strong soap odor.
(B) Pathogens and pathogenicity The pathogens are mainly citrus brown rot and Phytophthora infestans, mycelia and chlamydospore are overwintering in diseased plants and soils in the sick, and the following year, the temperature is increased, rainfall increases, and old lesions are found in Hyphae continues to harm healthy tissues and produce sporangia, releasing zoospore, spreading with water, splashing through the rain, or spreading through the soil. Zoospore contacts fruit or invades from wounds or natural orifices and develop into mycelia. The incubation period is generally 2 to 3 days. High temperature (15 ~ 35 °C), rain, soil water, root-neck cracks or wounds, fruit mechanical injury or insect injury are conducive to disease. In the rice field, the summer orange orchard is heavier than the hilly soil and the summer orange orchard, with a large degree of canopy closure, is heavier than the summer orange orchard with good ventilation conditions. The old summer orange orchard is heavier than the Xinxia orange orchard.
(C) Prevention and Control Measures To clear the drainage ditch, the result is to support the fruit branches well and prevent multiple fruit branches from sagging together, so as to improve the ventilation and light transmission conditions of the orchard, reduce the groundwater level and the humidity of the orchards, and improve the survival conditions of the pathogens.
Do a good job in orchard hygiene and reduce the number of pathogenic bacteria. Elimination of pests and branches and winter deciduous fruit drop, burning or buried deep outside the park. 60 to 100 kg of lime is applied per mu of orchard to carry out soil disinfection and adjust the pH value of garden soil. After scraping the cracked skin caused by citrus split skin disease or citrus foot rot, the trunk was smeared with lime sulfur, Bordeaux mixture, or whitening agent to suppress overwintering pests in the split skin.
Improve the disease resistance of summer orange plants. In spring and summer, the application of dried fruit cake 2 ~ 3 kg + urea 0.2 ~ 0.3 kg + calcium magnesium phosphate fertilizer 2 ~ 3 kg, to meet the needs of the nutritional needs of Huaguo same tree. Do a good job of thinning and fruit thinning to reduce plant burden. Scientific application of foliar fertilizers, such as vigorously growing summer orange trees, can be sprayed before the spring tip paclobutrazol or uniconazole + potassium dihydrogen phosphate, accelerating the spring shoot mature, as soon as possible into the functional leaf stage.
Epidemic prevention and control. The control of leafhoppers or elephant pests can be used to spray insects, kill insects, sweep insects or eliminate pungent insects to reduce insect damage. Spraying 80% schisomide WP or 72% bensulfan Manganese Zn wettable powder or 72% metalaxyl MnZn 500 to 600 times to prevent and control epidemic diseases.
The dense plants were cut in time, and the tree crowns were cleared to open the "skylight" and the decayed branches were retracted. (Author: Lu Sheng into the unit: Jiangyong County, Hunan Province pomelo Institute)
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