What are the common diseases of lettuce? A comprehensive guide
What are the common diseases of lettuce? Here is an introduction. When lettuce is produced in greenhouses in winter, it is prone to many diseases. Several common diseases of lettuce and their control measures are summarized as follows: Sclerotinia rot mainly damages the base of the stem. In the early stage, the diseased part is yellowish brown to brown and water-soaked, then spreads to the entire stem, causing the stem to rot or extending upward...
What are the common diseases of lettuce? Here is an introduction
When lettuce is produced in greenhouses in winter, it is prone to many diseases. Several common diseases of lettuce and their control measures are summarized as follows:
Sclerotinia rot mainly damages the base of the stem. In the early stage, the diseased part is yellowish brown to brown and water-soaked, then spreads to the entire stem, causing the stem to rot or extending upward and causing leaf rot, and finally the plant wilts and dies. When humidity is high, dense white cottony mycelial masses are produced, which later become black, mouse-dropping-shaped sclerotia.
Control methods: After harvest, thoroughly remove diseased residues and fallen leaves and carry out deep plowing. Reasonable close planting to reduce field humidity. Before transplanting, spray the transplanting holes with 25% triadimefon wettable powder. For chemical control, 40% flusilazole emulsifiable concentrate 3000-fold solution, 50% iprodione wettable powder 1500-fold solution, and 25% prochloraz emulsifiable concentrate 1000-1500-fold solution can be sprayed, focusing on the stem base and basal leaves, once every 7-15 days, for 2-3 consecutive sprays.
Downy mildew mainly damages leaves. Generally, the lower leaves are affected first and gradually spread upward. In the early stage, pale yellow nearly round or polygonal lesions appear on the leaves. When moist, white mold grows on the lesions on the underside of the leaves, and in severe cases the mold spreads to the upper surface of the leaves. Later, the lesions join together and turn yellowish brown, and the plant dies.
Control methods: After harvest and before transplanting, thoroughly clean up diseased residues and fallen leaves, plant at a reasonable density, strictly prohibit flood irrigation, drain promptly after rain, and reduce field humidity. For control agents, 72.2% propamocarb 600-fold solution and 50% dimethomorph 1500-fold solution can be used, sprayed on the underside of the leaves, at an interval of 7 days, for 2-3 consecutive sprays.
Gray mold can occur at the seedling stage and the adult plant stage. When it occurs at the seedling stage, the affected stems and leaves show water-soaked rot. When it occurs at the adult plant stage, it starts from the leaves near the ground, initially showing water-soaked irregular lesions, which later expand and turn brown, with the base appearing reddish brown. In severe cases, it rots upward from the base, and the stems and leaves wilt. When humidity is high, grayish brown or grayish green mold layers are produced on the diseased parts. When the weather is dry, the diseased plants gradually dry up and die, and the mold layer changes from white to gray to green.
Control methods: Strengthen management at the adult plant stage, increase ventilation, and reduce air humidity as much as possible. Once diseased plants are found, remove them promptly, take them out of the greenhouse, and destroy them. Before transplanting, use 50% procymidone wettable powder 1000-fold solution to spray the greenhouse soil, walls, greenhouse film, etc. for surface sterilization. For chemicals, Enzemei 1000-fold solution, Shijiale 500-fold solution, etc. can be used, once every 7 days, for 2-3 consecutive sprays.
Leaf scorch mainly damages leaves, mostly starting from the outer leaves or the edges of the heart leaves. In the early stage of infection, brown necrotic patches appear on the leaf edges. As the disease develops, the leaf edges become scorched and withered, the leaf color becomes lighter, and finally the whole plant wilts and dies.
Control methods: Keep the soil moist and at suitable water content, prevent the field temperature from being too high or too low, advocate the use of enzyme bacterial fertilizer, improve soil physical and chemical properties, and avoid excessive watering and fertilizing. For chemicals, 14% copper amine ketone aqueous solution 350-fold solution, 72% agricultural streptomycin sulfate 2000-fold solution, etc. can be used, sprayed once every 7 days, for 2-3 consecutive sprays.
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