First, lettuce gray mold
1. Symptoms Botrytis cinerea mainly affects the leaves and stem bases, and the seedlings are mostly affected by stems and leaves close to the ground. After colonization, the disease begins from the old leaves. The diseased part is water-stained lesions, and the leaves turn yellow and die; the diseased stems rot, the gray mold of the dense mice, and the entire base near the ground is infested in severe cases, causing the plants to wither.
2. Prevention
(1) Select healthy plants to keep seeds, select seeds with salt water (salt 0.5kg plus water 5kg) before planting, and remove the sclerotia mixed with seeds.
(2) Remove old leaves, improve ventilation conditions, strengthen ventilation, and reduce disease.
(3) Covering cultivation with plastic film, rational fertilization, increasing application of phosphorus and potassium fertilizer, cleaning the pastoral, and removing the central diseased plant.
(4) For the prevention and treatment of chemicals, the following agents can be sprayed, 50% more moldy wettable powder 1000-1500 times liquid; or 50% moldy mildew wettable powder 1000-1500 times liquid; or 50% profit (isobacteria) · Fu) wettable powder 800 ~ 1000 times liquid.
Second, lettuce soft rot
1. Symptoms Soft rot occurs mostly in the late growth stage. The pathogen is bacteria, and the diseased residues, fertilizers and insects in the soil can carry bacteria. When the autumn-sown lettuce enters the ball-forming period and the harvesting period, the appearance of the stems and leaves is not abnormal, and the pathogens are invaded by the wounds, and the disease is easy to occur in the early autumn. The infected plants wilted during the day and returned to normal in the evening. In severe cases, the night wilting could not be restored. Anatomically observed, the stem of the stem was hollowed out, stenching, and finally the stem rotted and died.
2. Prevention
(1) High ridge cultivation to avoid flooding;
(2) After spraying, spray 95% CT disinfectant aqueous solution (copper acetate) 500 times, or 14% lycopene copper solution 350 times;
(3) In the early stage of the disease, you can use 45% Dysonium water 1000 times solution, 1 million units of agricultural streptomycin 5000 times solution, or 1 million units of new phytomycin 4000 times solution, spray once every 7 to 10 days. , spray 2 to 3 times in a row, pay attention to the part near the bottom to control the disease.
Third, lettuce leaf blight
1. Symptoms Leaf blight mainly harms the leaves, and the lesions are irregularly grayish brown to dark brown. The edges of the leaves are yellowish brown, and black spots on the lesions are scattered, that is, the pathogens are conidia. Rapid development under low temperature and high humidity conditions. In addition, during the daytime drought, nighttime exposure, when the temperature is too high or too low, the growth is poor, the disease resistance is reduced, and the disease is aggravated.
2. Prevention
(1) Select disease-free seeds or seed disinfection, and use the mother roots to select disease-free petioles and stems and leaves to prevent bacteria. The use of two-year-old Chen seeds has certain disease-preventing effects. The new seeds must be disinfected and used. They can be soaked in warm water at 48-49 °C for 30 minutes. The seeds are continuously stirred during soaking, so that the seeds are evenly heated. Immediately after soaking seeds, they are cooled into cold water. This method has a little influence on the germination rate of the seed, and generally reduces the germination rate by about 10%, but the disinfection is relatively thorough.
(2) Elimination of diseased plant residues, the diseased leaves can be removed at the beginning of the disease to reduce the source of the disease.
(3) Chemical control, to prevent the main, after planting slow seedlings, spray Bordeaux mixture once every 10 to 15 days (1:0.5:200), or 65% Dyson zinc WP 500 times, or 45 % sensen ammonium water 1000 times solution, or 75% chlorothalonil WP 500-800 times solution, or lime copper powder (80 parts lime, 20 parts copper sulfate) or lime copper sulphur powder (30 parts lime, 10 Part of copper sulfate, 10 parts of sulfur powder), or 10% of high water suspension agent 1500-2000 times liquid.
1. Symptoms Botrytis cinerea mainly affects the leaves and stem bases, and the seedlings are mostly affected by stems and leaves close to the ground. After colonization, the disease begins from the old leaves. The diseased part is water-stained lesions, and the leaves turn yellow and die; the diseased stems rot, the gray mold of the dense mice, and the entire base near the ground is infested in severe cases, causing the plants to wither.
2. Prevention
(1) Select healthy plants to keep seeds, select seeds with salt water (salt 0.5kg plus water 5kg) before planting, and remove the sclerotia mixed with seeds.
(2) Remove old leaves, improve ventilation conditions, strengthen ventilation, and reduce disease.
(3) Covering cultivation with plastic film, rational fertilization, increasing application of phosphorus and potassium fertilizer, cleaning the pastoral, and removing the central diseased plant.
(4) For the prevention and treatment of chemicals, the following agents can be sprayed, 50% more moldy wettable powder 1000-1500 times liquid; or 50% moldy mildew wettable powder 1000-1500 times liquid; or 50% profit (isobacteria) · Fu) wettable powder 800 ~ 1000 times liquid.
Second, lettuce soft rot
1. Symptoms Soft rot occurs mostly in the late growth stage. The pathogen is bacteria, and the diseased residues, fertilizers and insects in the soil can carry bacteria. When the autumn-sown lettuce enters the ball-forming period and the harvesting period, the appearance of the stems and leaves is not abnormal, and the pathogens are invaded by the wounds, and the disease is easy to occur in the early autumn. The infected plants wilted during the day and returned to normal in the evening. In severe cases, the night wilting could not be restored. Anatomically observed, the stem of the stem was hollowed out, stenching, and finally the stem rotted and died.
2. Prevention
(1) High ridge cultivation to avoid flooding;
(2) After spraying, spray 95% CT disinfectant aqueous solution (copper acetate) 500 times, or 14% lycopene copper solution 350 times;
(3) In the early stage of the disease, you can use 45% Dysonium water 1000 times solution, 1 million units of agricultural streptomycin 5000 times solution, or 1 million units of new phytomycin 4000 times solution, spray once every 7 to 10 days. , spray 2 to 3 times in a row, pay attention to the part near the bottom to control the disease.
Third, lettuce leaf blight
1. Symptoms Leaf blight mainly harms the leaves, and the lesions are irregularly grayish brown to dark brown. The edges of the leaves are yellowish brown, and black spots on the lesions are scattered, that is, the pathogens are conidia. Rapid development under low temperature and high humidity conditions. In addition, during the daytime drought, nighttime exposure, when the temperature is too high or too low, the growth is poor, the disease resistance is reduced, and the disease is aggravated.
2. Prevention
(1) Select disease-free seeds or seed disinfection, and use the mother roots to select disease-free petioles and stems and leaves to prevent bacteria. The use of two-year-old Chen seeds has certain disease-preventing effects. The new seeds must be disinfected and used. They can be soaked in warm water at 48-49 °C for 30 minutes. The seeds are continuously stirred during soaking, so that the seeds are evenly heated. Immediately after soaking seeds, they are cooled into cold water. This method has a little influence on the germination rate of the seed, and generally reduces the germination rate by about 10%, but the disinfection is relatively thorough.
(2) Elimination of diseased plant residues, the diseased leaves can be removed at the beginning of the disease to reduce the source of the disease.
(3) Chemical control, to prevent the main, after planting slow seedlings, spray Bordeaux mixture once every 10 to 15 days (1:0.5:200), or 65% Dyson zinc WP 500 times, or 45 % sensen ammonium water 1000 times solution, or 75% chlorothalonil WP 500-800 times solution, or lime copper powder (80 parts lime, 20 parts copper sulfate) or lime copper sulphur powder (30 parts lime, 10 Part of copper sulfate, 10 parts of sulfur powder), or 10% of high water suspension agent 1500-2000 times liquid.
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