The diseases of spring lettuce mainly include downy mildew, viral disease and sclerotinia.
First, downy mildew:
The disease is one of the major diseases in the current production of lettuce. It mainly infects the leaves. After the onset of disease, the seedlings turn yellow and die, and the adult disease occurs. The disease develops from bottom to top. At the beginning of the period, yellowish-yellow subrounded or polygonal lesions appeared on the leaves. When the damp spots appeared, white moldy leaves grew, and sometimes the moldy layer could spread to the front of the leaves. The late lesions turn into yellow-brown and connect into pieces, causing the whole leaves to dry, and sometimes the bacteria can infect the stems and cause the stems to become dark.
Control methods: Use 72% Du Bang Ke Lu 600-800 times or 58% metalaxyl manganese zinc 500 times spray, 7-10 days once, pay attention to alternate medication.
Second, the virus disease:
Both the seedling stage and the adult stage can be diseased, manifested as mosaic, malformation, yellowing, dwarfing, necrosis and other symptoms. The diseased plant is stunted and the yield and quality are severely reduced. The leaves showed variegation of leaf shades, showing signs of bright veins, spots, and mosaics. The diseased leaves were shriveled, the leaf margins were irregular or nicked, there were dwarfs of varying degrees, and yellow and brown necrotic spots appeared on the leaves. Or fine veins turn brown.
Control methods: soaking seeds with warm soup or seedlings with trisodium phosphate before sowing, in addition, virus A, plant disease and plant growth regulators can be used to enhance the resistance of the plants.
Third, Sclerotinia:
It usually develops from the base of the stem and gradually spreads upwards and downwards, causing skin rot. The surface of the lesions were cotton-like hyphae with black murine bacillus nucleus inside, and the upper part of the diseased plants quickly wilted and died. After the storm spreads, the bacteria invade from the senescent parts of the plant. Low humidity, high density, can promote disease.
Control methods: Use 50% of quick-lying 1500 times liquid or 40% of sclerotium net 1000-1500 times liquid spray.
Insect pests are mainly aphids and can be treated with 10? Imidacloprid 800?1000 times.
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