The scientific name of Ipomoea aquatica Forsk. Alias ​​bamboo dish, spinach, rattan dishes. Is an annual or perennial herbaceous plant of the genus Convolvulaceae sweet stems and leaves. According to the adaptability to water, it is divided into two types: drought, waterlogging and waterlogging. Use whole plant and root medicine. With heat detoxification, diuretic, hemostatic effect. It is cultivated everywhere. Variety 2051635 Symptoms are commonly known as "decrease" and "rot." The main damage is the tender stems of the seedlings. Seed germination before seedbed emergence causes bad species. After the cotyledon was unfolded, the seedlings showed light brown water stains, followed by the base rot. The cotyledon did not wither and the seedlings had fallen. The whole plant quickly died. Near the diseased plant became the center of the disease, the nursery bed collapsed in large and small, and the diseased seedlings fell into pieces.
Pathogen Pythium aphanidermatum (Eds.) Fitzp. Pythium, called fruit, is a flagellarium fungus. The mycelium grows flourishingly, showing a white cotton floc; the mycelium is colorless, without a diaphragm, and has a diameter of 2.3-7.1 μm. Mycelia and cyst stalks are not distinctly different. The sporangia are filiform or branched, or irregular, with a size ranging from 63-7254.9 to 14.8 (μm). Blisters spherical, containing 6-26 zoospore. The oocyte has a spherical shape with a diameter of 14.9-34.8 μm. Male bag-shaped to wide stick-like, with silk or different filaments, more than one, size 5.6-15.47.4-10 (F2m). The oospore is spherical, smooth, and less than full, with a diameter of 14.0 to 22.0 μm. The bacteria occur at a high frequency in places where the average annual temperature is high. In addition, P.spinosum Saw is called Pythium spp., which belongs to the flagellin subfamily fungus and is also the pathogen of the disease.
Transmission routes and pathogenic conditions The oocysts overwinter in the top layer of 12-18cm and survive long-term in the soil. In late spring, the sporangia germinate under suitable conditions to invade the host with zoospores or buds. In addition, spore sacs can also be produced by the mycelium of living in the earth and rot in the soil, causing the zoospores to invade the seedlings to cause tripping. Reinfection in the field is mainly due to the production of sporangia and zoospores on diseased seedlings, causing more serious losses by sprinkling irrigation water or rain onto roots close to the ground. After invading bacteria, the bacteria expands in cortical parenchyma cells, hyphae spreads among cells or cells, and then forms oospores in diseased tissues. The growth of the bacteria is suitable for the temperature of 15-16°C, and the temperature is higher than 30°C. The temperature is suitable for 10°C. The low temperature is unfavorable to the growth of the host, but the germs can still be active, especially the low-temperature and high-humidity conditions during the nursery period are conducive to disease. When the seedling cotyledon nutrient is basically used up, the new root is not yet solid before the disease period. At this time, true leaves are not extracted, carbohydrates cannot increase rapidly, and disease resistance is weak. In case of rain or snow, even cloudy or cold currents invade, the ground temperature is low, photosynthesis is weak, respiration of seedlings is enhanced, consumption is increased, and young stem cells are induced. Elongation, cell wall thinning bacteria invade. Therefore, the disease mainly occurs in seedlings with 1-2 leaves. Fuzhou area will be the incidence of sowing from March to June, especially in March-April nursery or greenhouse hotpot nursery susceptible to disease. The occurrence of the disease is closely related to the microclimate of the seedbed, among which are mainly humidity, seedling depression, over-seeding and non-ventilation, excessive bed soil moisture in the watering, and overheating of the seedbed. Back-season cultivation or summer nursery beds suffer from low-temperature, high-humidity weather or heavy rainfall.
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