Disease at the seedling stage is a general term for a variety of physiological diseases and invasive diseases during rice nursery. It is also called gill disease. Physiological rotting refers to bad environmental conditions caused by rotten species, rotten buds, black roots, blue and yellow withered dead seedlings and other symptoms; infestation rotten roach refers to cotton rot disease and damping-off caused by dead bacterial disease symptoms. Northern rice growing areas are often attacked by low temperature and cold weather. The annual incidence of gill disease is between 10% and 23%. Symptoms: Physiological rotten roaches are: 1, rotten species, refers to the seed germination that is rot; 2, rotten buds, refers to just germination of young buds curled into a hook-like, not the roots to death, or plunged into the mud and die , Or the formation of drifting; 3, black root, refers to the roots of seedlings black rot, the leaves gradually withered; 4, blue and dry, refers to the seedlings green not yellow suddenly died, the base is not rot, the seedlings are not easy to pull up; 5, dry, means The seedlings slowly turn brown and yellow and die. The roots are rotten and the sickness is easy to pull up. Infectious rot is: 1, cotton rot, aquatic seedlings can be sown 5 to 6 days can occur, seedling height of about 3 cm when heavy, damage to the larvae and young shoots, a small amount of seed shell rift or bud base The milky white gel gradually grows out of radial white flocculent mycelium and gradually develops rust, greenish brown, or brownish brown; the seeds do not rot when germinating, or the roots of diseased seedlings rot and die. The disease occurred from spot to film, and when severe, it died. Bacterial blight, wet seedlings, dry seedlings, and film seedlings were most common in the fields. The symptoms were as follows: 1 bud rot. The young shoots of the bud before emergence were browned, twisted, rotted, and died. A white mold layer was later generated; Seedlings from the needles to the two-leaf stage, the heart is yellow, the base is brown, sometimes brown spots appear on the leaf sheath, the moldy layer is produced at the base of the stem, and the seedlings are easy to pull off; 3 yellow wither, the seedlings occur from 1 leaf to 3-4 leaves. The lower leaves began to wilt and wilted, the root hairs were scarce, and the bases turned brown and soft rots. 4 Scabs occurred mostly before and after the 3-leaf stage. The leaves of the seedlings or the upper leaves were rolled into willow-like leaves with blue-gray, rare root hairs, and the bases were browned later. Soft rot, easy to cluster: Pathogens and occurrence of physiological rot are mostly due to poor seed quality, uneven heat and cold during germination, poor sowing quality, excessive water storage, lack of oxygen and suffocation, as well as cold or post-cold temperature changes at seedling stage. However, black root is caused by earthworms: fertilizer is too large, water is too deep, and large amounts of hydrogen sulfide, iron sulfide, and other reducing substances poison the seedlings. Bacillus spp. of infective gills is mainly caused by the infection of cotton molds, fungal infections such as Pythium spp.; Rhizoctonia mainly caused by Fusarium spp. and Rhizoctonia solani, and pathogenic bacteria can be found in soil. In the medium to long-term life, the mycelium, oospores, sclerotia are allowed to overwinter in the soil or in the sick, and are transmitted by water currents and air currents; Rhizoctonia solani and hyphae are used for wintering in diseased bodies and soil to flow water. Transmission, mainly through wounds, young tissue invasion. Prevention and control measures Prevention and treatment of rice seedling disease should adopt comprehensive measures to improve seedlings, improve seed quality and germination techniques, strengthen management of farmland, and supplement with chemical control. According to local conditions, plastic film seedlings, floppy disk seedlings and dry nursery seedlings are used. Water seedlings are not recommended. Putian chose to shelter the sun, flat terrain, medium fertility, convenient irrigation and drainage plots. Keep seed, seed storage, drying, and seed selection to increase seed germination rate. Seed soaking in warm water (55°C for 10 minutes) or soaking with chemicals (50% carbendazim 800 times for 3 days). During germination, the temperature is stable at more than 10°C to prevent over- or under-concentration, ensure that the buds are uniform, homogeneous and strong, and strengthen the cold resistance of the seedlings. Strengthen seedling management, fine land preparation, ensure bed leveling, bed temperature and permeability; choose temperature when stable above 10°C; sow scientifically, use water temperature to protect seedlings; apply reasonable fertilizer, pay attention to NPK combination, increase organic application Fertilizer, avoid nitrogen, enhance seedling disease resistance. Chemical control, timely medication in the early stage of disease, pouring 75% of dexamethasone 1000 times solution, 50% of dexamethasone 800 times solution, 5.5% of soaking spirit 3000-5000 times solution, 58% of metalaxyl manganese zinc 1500 times Liquid, 2 to 3 kg per square meter.
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