Disease Recognition and Prevention of Lettuce in Sunlight Greenhouse
First, lettuce gray mold
1. Symptoms Gray mold mainly damages the bases of leaves and stems, and seedlings suffer more damage on stems and leaves close to the ground. After the colonization, the disease started from the old leaves. The diseased part became a water-stained lesion, the leaves turned yellow and died, the diseased stems were rotted, the dense-born mouse was gray mold, and when severe, the entire base of the ground was infested and the plants withered.
2. Control and selection of healthy strains. Seeds were sowed with salt water (0.5 kg of salt and 5 kg of water) before sowing, and the sclerotia mixed with the seeds were removed. Remove old leaves, improve ventilation, increase ventilation, and reduce disease. Rational fertilization, increase phosphorus and potassium fertilizers, clean the pastoral areas, and remove diseased central diseased plants. Chemicals can be sprayed with the following agents: 50% carbendazim WP 500 times, or 50% thiophanate WP 500 times, or 50% chloramphenicol wettable powder 400 times, or 65% Dyson Zn WP 400 times, or 50% TBX 800 times, or antibacterial "407" 800 times, or Lithium: copper sulphate: water Bordeaux mixture 1:2:200-240, 7 Spray 10 times a day for 10 days, spray 2 or 3 times continuously, or 2,000 times liquid based on special bacteria.
Second, lettuce soft rot
1. Symptoms of soft rot in the late growth stage, the pathogen is bacteria, soil, fertilizers, insects can carry bacteria. When the lettuce was sown in the autumn and harvesting seasons, there was no abnormality in the appearance of leaf stems. Pathogens are invaded by wounds and are susceptible to attack at high temperatures in early autumn. The infected strain was wilted during the day and returned to normal in the early evening. Severe wilting at night could not be restored. Anatomical observations revealed that the essence was hollowed out and odor was emitted, and finally the stem was rotted and died.
2. Control spraying 40% organic ketone 800 times successively after colonization. At the beginning of the disease, the following agents were sprayed, and the part near the bottom was sprayed to control the disease. 50% Daisen ammonium water agent 800 times, or 200 ~ 300 units of streptomycin, or 300 units of chloramphenicol, spray once every 7 to 10 days, continuous spray 2 ~ 3 times.
Third, lettuce rot
1. Symptoms The rot disease causes water-stained lesions on the leaves of 2 to 3 layers on the surface of the knotted leaves, and then decays to the entire leaves and migrates to the inner leaves. From the beginning of the ball, the more severe the frost damage, the heavier the disease, and the heavier parts of the leaf juice soluble solids content. In the period of entering the ball, the viability of the roots will decline, and if the disease continues to harvest, it will be seriously damaged.
2. Prevention and replantation of cultivated lettuce should start from the beginning of the ball to pay attention to complete pest control, in order to avoid pests damage the nodule, causing disease. Winter lettuce cultivation should pay attention to prevent the occurrence of frost damage, can take greenhouse insulation, planting large seedlings, shorten the growth period, reduce the incidence of disease. At the beginning of the disease, spray 40% organic ketone 800 times.
Four, lettuce leaf blight
1. Symptoms Leaf blight mainly damages the leaves, and the lesions are irregularly gray-brown to dark brown. The edges of the leaves are yellow-brown and black dots are scattered on the lesions, which are pathogenic conidia. Rapid development under low temperature and high humidity conditions. In addition, the drought during the day and the dew exposure at night, when the temperature is too high or too low, the growth is poor, the disease resistance is reduced, and the disease is aggravated.
2. Control selection of disease-free seed or seed disinfection, seedlings should be selected for disease-free leaf stalks and stems and leaves to prevent colonization. The use of Chen seeds for two years has a certain disease-preventing effect. The new seeds must be used after disinfection. The seeds can be soaked in warm water of 48-49°C for 30 minutes. When soaked, the seeds are constantly stirred to make the seeds evenly heated. Immediately after soaking, cool in cold water. This method has a little effect on the seed germination rate. Generally it reduces the germination rate by about 10%, but the disinfection is more thorough. In the early stages of disease, diseased leaves can be removed. After planting the seedlings, spraying once every 10 to 15 days. The following agents can be sprayed: Bordeaux mixture (11:0.8:2000), or 65% zeocin zinc WP 500 times, or 50% dexamethasone 1000X, or 75% chlorothalonil 500-800 Diluent, or lime powder (80 lime, 20 parts of copper sulfate powder) or ketal sulfur powder (30 lime, 10 parts of copper sulfate powder, 10 parts of sulfur powder).
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