Control strategy of dead seedlings of eggplant
Eggplant has a deep soil layer, is rich in organic matter, and has good permeability in sandy loam soil. If it is planted in soil with high viscosity, it will easily induce rot. Eggplants have large leaves and strong transpiration. They require large amounts of water, but they are afraid of cockroaches. Therefore, management can not make eggplants lack of water, nor can watering be too large, causing water accumulation in the fields. Otherwise, it is easy to cause hypoxia in the roots, and the product of anaerobic respiration can cause poisoning in the roots and cause rot.
First, the disease
1, tripping disease. Eggplant seedlings can be damaged before or after unearthing. Unripe seedlings develop, embryos and cotyledons turn brown and rotten, and seedlings die. After the emergence of the seedlings, the base of the stem was initially water-stained. Afterwards, the diseased part became yellow-brown and shrank to a shallow shape. The disease develops rapidly, often before the cotyledon has wilted, and the seedlings are folded and affixed to the ground. However, the seedlings are still blue-green, so they are called cataplexy. At low temperatures and high humidity, a layer of white cotton flocculent mycelium grows on the surface of the host's diseased body and nearby soil. In the seedbed, only the individual seedlings began to appear. After a few days, the seedlings spread around and spread to the surrounding area, eventually causing the seedlings to stumble.
pathogen. It is Pythium trichoderma in the genus Pythium. Mycelium developed, many branches, colorless and no diaphragm. The cystic stalks were not distinctly differentiated, and the sporangia were terminal or apical, forming a swollen tube, and some with a fissure-like branch. The zoospore is a double flagellum and kidney-shaped. After swimming for a short time in the water, it turns into a circular resting spore. After germination, the germinating tube invades the parasite.
2, blight. More in the bed temperature higher seedbed or nursery later in the disease. At the early stage of disease, the elliptic dark brown spots were found at the base of the seedlings. Early diseased seedlings wilted during the day and recovered sooner or later. Afterwards, the diseased part gradually sag, expands around the stem for a week, and it shrinks and dries up. Finally, the plants die. As the diseased plants are mostly erect and die, they are called blight.
Pathogen: Rhizoctonia solani of the genus Deuteromycotina. The mycelium was colorless in the early stage and gradually turned pale brown at the later stage. The branches showed a right angle, the base of the branches shrank, and there was a septum not far from the branches. Sclerotia, sclerotia without a certain shape, light brown to dark brown, loose texture, rough surface.
Second, the prevalence of diseases and the main determinants
1, climatic conditions. The microclimate conditions of the seedbed at low temperature and high humidity are important factors leading to disease occurrence. The suitable temperature for eggplant growth is 22-23°C. The optimum seedling temperature is 20-30°C. In this temperature range, the seedlings grow well and have strong disease resistance. On the contrary, too high or too low temperatures can easily lead to disease. If the temperature is too low, it is prone to damping-off, the temperature is too high, the seedlings are too long, and blight easily occurs. The air has a high humidity, especially when the humidity of the bed and soil is high, and the seedlings are seriously affected. Because of the growth of germs, germination and invasion of sclerotia all require higher humidity and a certain amount of moisture. When the humidity is high on the bed, the growth of seedling roots is unfavorable and the resistance to disease is reduced, which is conducive to the spread and spread of the disease; the light is sufficient, the seedlings have strong photosynthetic activity, strong growth, and strong resistance to disease. If the lack of light, seedling growth is weak, it is easy to get sick.
2, host growth period. The nutrients in the cotyledon of seedlings have been depleted and the new roots have not yet been established. The young stems are in danger of becoming susceptible during the period of no lignification.
3, seedbed management. The low humidity in the seedbed and poor root growth of the seedlings are more serious. The bed is poorly ventilated and light, toxic gases are accumulated more, and it is easy to induce the disease.
4, the nature of the soil. In the poor and viscous soils, the diseases are heavier, while the sandy loam with rich organic matter and good permeability is less likely to occur.
Third, prevention and control strategies. The main cultivation and management, supplemented by chemical control.
1, agricultural control. Carefully select the bed site and build the bed scientifically. It is required that the seedbed irrigation is convenient and the seat is sunny, which is convenient for controlling the temperature. Use rotten fertilizer to create a good condition conducive to the growth of eggplant. Strengthen management, pay attention to insulation, control humidity, timely ventilation and light transmission, promote seedling growth. Implement rotations to achieve a rotation of more than 4 years.
2, deal with the soil. Usually 2-3 weeks before sowing, the soil is first loosened, 450 ml of formalin per square meter, 20-30 kg of water, poured on the bed, and then covered with plastic film for 4-5 days; Remove the film, loosen the bed soil, allow the liquid to fully evaporate before planting.
3, where conditions can be used to nurse seedlings.
4, seed treatment. Warm soaking: soaking in warm water at 55°C for 15 minutes; dressing seed or soaking seed; 40% seed dressing or seed dressing WP, 80% chlordane wettable powder, dosage for seed dressing 0.2% of seed weight. In addition, the application of 25% metalaxyl wettable powder and 70% mancozeb WP to 9:1 mixing, and then immersed in water 1500 times soaked, dried after sowing.
5, pharmaceutical control. If a small number of diseased seedlings have been found on the seedbed, they should be promptly removed and sprayed to protect against the spread of disease. The agent can be sprayed with 75% chlorothalonil wettable powder 1000 times or 70% mancozeb wettable powder 600 times.
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