2019年11月6日星期三

The Common Diseases and Prevention of Watermelon during Storage and Preservation Period

The major hazards of watermelon during the storage and preservation period are anthracnose, penicillin rot, cold injury, high co2 and low o2 damage. Among them, anthrax and penicillin rot are fungal diseases, and others are physiological diseases. These diseases cause the decline of the quality of watermelon products, and they cause a large amount of rot, which is a harmful factor that cannot be ignored in the storage and preservation of watermelon. After three years of observation and observation of storage and preservation of watermelon, the symptoms, causes, and prevention and control methods of the disease were summarized as follows. First, anthrax. Anthracnose is one of the common diseases during the preservation period of watermelon. The majority of its pathogenic bacteria have been infected and invaded before the ripening of watermelon. After mature harvest of watermelon, after pre-cooling, immediately stored at a suitable low temperature condition, or treated with a bactericide, the original small lesions develop slowly and diffusely, while the larger lesions are inhibited. If stored above 15°C, the infected watermelon quickly shows symptoms. At the beginning of the disease, pale brown spots appeared on the melon surface, and after the lesions gradually expanded, the color of the surface of the lesions was staggered, and the melon flesh was also sagged with soft rot, resulting in decay and unbearable consumption. Control methods: (1) Spraying 800 times of carbendazim for 7-15 days before harvesting is effective; (2) After harvesting watermelon, 300-600 times of carbendazim is used to dip melon for 10 minutes, dried and stored, and the effect is good. (3) The use of appropriate low-temperature storage can effectively control the development of anthrax at a temperature of 5-6°C. Second, penicillin rot. Penicillic rot is a frequent disease during the storage period of watermelon. The pathogen comes from the watermelon itself and storage place. After harvesting, watermelon touches serious crushing and the incidence is heavier. Penicillium mainly invades guadi and wounds. After gutty infestation, it begins to appear as small white spots. After 10-15 days, the spot expands to form a number of grayish white mycelia. Guatyum has a layer of villous hyphae. Causes Guaty to turn black. Secondly, the watermelon is wounded due to injury or other pests. After being infected by Penicillium, the watermelon initially displays white spots. After 3-5 days, the spots expand, forming white hyphae, and the mycelium can cover the entire lesion after concatenation. The lesion gradually spread outwards, from the surface of the skin to rotten and melon, and there was mildew and taste, and it was not edible. Control methods: The prevention and treatment of penicillin rot disease is basically the same as the prevention and treatment of anthrax. The main reason is to choose disease-free, high-quality fresh watermelon as storage material, pick and place gently, avoid violent vibration during transportation, and minimize wounds. To reduce the incidence of Penicillium infection. In addition, the place for watermelon storage should be 3 days before storage of the watermelon, fumigation with sulphur (10 g/m3), and then closed for 2 days, then ventilation can be. Third, cold damage. Cold damage is above the freezing point, and it is not suitable for physiological and metabolic disorders of fruits and measles caused by temperatures. The critical temperature of chilling injury of watermelon is different due to its variety and origin, and its sensitivity to chilling injury is different. When the storage temperature is lower than the suitable temperature of watermelon, cold injury is easy to occur. For example, the mid-late and late-maturing harvest of Fengshou No. 1 had a chilling injury when stored at temperatures below 5°C. At the beginning of the disease, green varieties of melon surface appear irregular small and shallow dark green spots, then gradually expand, begin to sag, so that the melon surface forms "pock face" shape, when the melon meat is thick, the outer layer becomes soft and gradually inward Layer expansion, also water-like, easy to be infected by bacteria quickly ulceration. Control methods: (1) Spraying 0.4cl2 solution 7-10 days before harvest can increase the content of Ca2+ in the tissue and enhance the resistance of the watermelon. (2) Storage at a suitable temperature can avoid cold damage. For example, the mid-late and late-maturing harvest of Fengshou No.1, the storage temperature is 7.2–12.5°C, and the late-maturing disease-resistant black giant hepatoides, the storage temperature is 5-10°C. (3) Moderate dry conditions, such as relative humidity of 65-80%, are beneficial for disease control. (4) Selection of suitable maturity (8, 9 mature) watermelon storage can reduce the sensitivity to chilling injury. Fourth, high co2 and low o2 damage. Most of the high-co2 and low-o2 damage of watermelon occurred in the atmosphere storage. When the o2 in the atmosphere changed to 1%, or co2 was higher than 3-8%, the injury was easy to occur. In the early stage of victimization, the surface of the watermelon formed dark, small spots, and it gradually collapsed. Afterwards, it gradually expanded to form lesions with obvious boundaries and started to be immersed. In severe cases, the outer epidermis formed a thin layer of relatively brittle crust, and gradually wrinkled and cracked. The skin and melon are separated, and the lesions are eroded or have an alcoholic taste, especially the parts near the seeds are purple, the meat is hard and has toughness, but the flavor deteriorates. The victims suffered from large lesions that spread throughout the entire melon and eventually lost their food value. In controlled atmosphere storage, it is mainly to strictly control the climate change index in the environment. The moisture index of watermelon is o23%-5%, co20.5-2%. Generally every 7-12 days, the gas composition is detected by using the Aussigmatis gas analyzer. When the concentration of co2 increases in a short time, ventilation should be performed as soon as possible to restore the o2 concentration to the normal range, so that the poisoning of co2 can be reduced.

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