Rice dry nursery seedlings in the "weaning period" (leaf age before and after the two leaves in one heart) often appear dead seedling phenomenon. The typical symptoms are: the diseased seedlings first rolled up and showed a green stain. The diseased seedlings were easy to pull up, and the root tip or even the whole root system showed water-stained necrosis after pulling up. The whole condition was rapid and rapid, especially the dry nursery boring machine which had suddenly been ventilated from the both ends after a long period of rain and storm was the most serious. It could easily cause the seedlings to quickly appear as a “massive†or “spotted†death in a short period of time. Dry rice seedlings died during weaning. The internal cause was that the stored nutrients in the rice seeds had been depleted at this stage, and the root development was not yet perfect. The resistance to outside environment and climate conditions was the weakest, and the external temperature was the result of persistent low temperatures that led to seedling roots. been destroyed. If the drought-tolerant rice seedlings at the weaning stage meet the hypothermia attack, the various metabolic activities of the rice seedlings will be inhibited, the growth and development will be hindered, and the disease resistance will be reduced. Second, the extravasation of nutrients in rice roots will be exacerbated and the soil will become various. The proliferation and spread of germs provide a large amount of nutrients; the third is that the low temperature (4--15°C) can weaken the activities of other microorganisms that have inhibitory effects on Pythium in the soil, and it is still appropriate for the growth and reproduction of Pythium spp. Under dry conditions, soil permeability is good, which is conducive to aerobic Pythium activity and reproduction. In case of adverse environmental and climatic conditions, even if measures such as acid adjustment and disinfection are applied to the trampoline before rice is sown, the root system of rice seedlings will be destroyed to varying degrees. If the low temperature lasts for a long period of time and the intensity is high, the seedlings are chronically “yellow witheredâ€; if the low temperature persists for a short period of time, the seedlings are not dead, but after the storm, if the film is suddenly ventilated from both ends at high temperatures, the trampoline The internal temperature is still very high, but the humidity is rapidly reduced. The root water of the seedlings is far from supplying water to the leaves to evaporate. It is often due to water loss and metabolic disorders, leading to acute "greenish" dead seedlings. Regardless of the chronic “yellow dry†or acute “blue and dry†dead seedlings, the seedlings still stand upright after their death. From the above, it can be seen that dry rice seedlings die during weaning and must have three conditions: first, the soil of the seedbed contains Pythium bacteria; second, low temperatures and good ventilation (oxygen sufficient) provide for the proliferation and invasion of Pythium Advantageous environmental conditions; Third, suddenly turned to clear after low temperatures, membrane ventilation led to water supply and demand imbalance seedlings. In view of the conditions of the disease, it was found that the drought-induced seedlings of rice dry-up seedlings were still dead at the weaning stage. The following measures should be taken immediately: 1 Watering (or watering). If there are irrigation conditions, timely flooding inundates the bed surface. Otherwise, the seedbed water will be poured as far as possible. As long as the seedbed and air humidity are improved, the phenomenon of dead seedlings can be quickly alleviated. After the new roots of rice seedlings are well (or trifoliate), the water is drained and enters the moist management stage. 2 spraying. The use of “enexone†and “drought-sinking spirit†to spray water into dry-land boring machines can alleviate the disease and improve the quality of seedlings. 3 moisturizing. It is forbidden to suddenly remove the film and ventilate when the temperature is high after the cold storm, and it is even more important to not only open the membrane for ventilation. The film can be properly shaded on the membrane surface, or small slits can be ventilated and cooled around the membrane to try to maintain the trampoline in a highly humid environment and prevent dehydration of the seedling leaves.
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