Common diseases and control methods of spring lettuce
At present, it is the key period for the production management of spring lettuce, and it is also the high incidence period of common diseases. Recently, the technicians of the vegetable station in Dingzhou City of Baoding investigated the lettuce planting base in Taxuan Village and found that there are many problems. The diseases such as downy mildew, virus disease and crack are more common. Now introduce the field symptoms and prevention methods of common diseases to everyone, for reference by farmers.
First, the stem collapses in the middle and late stages of lettuce expansion, the inner stem is split longitudinally, and some are deep in the middle of the stem, and the cracked part is yellowish brown and perishable. The reason is that the water and fertilizer supply is uneven, the soil is too dry and too wet, and when the inner stem is close to maturity, the outer skin has been lignified. At this time, a large amount of water is poured, and the outer skin cannot be swollen and cracked.
Control method: scientifically manage the fertilizer and water, often keep the field moist, generally watering once every 10 days, and adding phosphorus and potassium fertilizer .
Second, downy mildew The disease is currently a major disease in the production of lettuce, mainly infesting leaves, the seedlings turn yellow and die after the onset of the disease, the onset of the adult stage, the leaves from the bottom up. The early leaves are pale yellow near-circular or polygonal lesions. When wet, the leaf back lesions grow white mildew, and sometimes the mildew can spread to the front of the leaves. In the later stage, the lesions turn to yellow-brown and connect into pieces, causing the whole leaves to dry up. Sometimes the bacteria can infect the stems, causing the stems to turn black.
The prevention and treatment method uses 72% Du Jie Kelu 600-800 times liquid or 58% metalaxyl manganese zinc 500 times liquid spray, 7-10 days once, pay attention to alternate medication .
Third, the virus can occur in both the seedling stage and the adult stage, which are characterized by various symptoms such as mosaic, deformity, yellow flower, dwarf, necrosis, and the diseased plant is poorly developed, which seriously reduces the yield and quality. The leaves are characterized by pale mottled leaves, bright veins, spots and mosaic symptoms, diseased leaves shrinking, leaf margins are not neat or nicks, varying degrees of dwarf, sometimes yellow and brown necrosis on the leaves Spots or fine veins turn brown.
The control method is to treat the seed with warm soup soaking method or trisodium phosphate before sowing. In addition, a plant regulator such as virus a, phytopathogenic pairing green wind 95 or alizarin can be used to enhance the resistance of the plant .
Fourth, sclerotinia sclerosis often occurs from the base of the stem, and gradually expands upwards and downwards, causing the epidermis to rot. There are cotton-like hyphae on the surface of the lesion, and there is a black rat fecal sclerotium. The upper part of the diseased plant quickly wilted and died. Through the wind and rain, the bacteria invade from the aging parts of the plants. Low temperature and humidity, high density, can promote the disease.
The control method is to use 50% of the speed of 1500 times of speed, or 40% of the sclerotia, 1000-1500 times of liquid spray .
5. The convulsions are characterized by slender stalks, elongated internodes, thin and small leaves, thick outer skin and less meat, and low food value. The first reason is that the supply of fertilizer is insufficient, especially the lack of base fertilizer, which inhibits the expansion of the fleshy stem. Second, the water supply is insufficient. In addition, factors such as excessive temperatures may also lead to convulsions.
Control method: Apply enough base fertilizer, water and fertilizer management should be appropriate, and the appropriate temperature should be mastered during the nursery period .
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