Winter lettuce is mainly used to control downy mildew, soft rot, and sclerotia. To control the greenhouse humidity, ventilation and disease prevention. 1. Downy mildew: Seed dressing with 25% metalaxyl WP with a seed weight of 0.3%; once the central diseased plant is found, use 40% diethylaluminium phosphate 200 times, 75% 100% Bai Miaoqing 500 times fluid, 25% Metalaxyl 800 times liquid, spray 50 kg per acre. 7 to 10 days once for 2 or 3 consecutive times 2, soft rot: timely removal of diseased plants, after removal of the hole can be filled with slaked lime to disinfect the seedlings, the early onset with 72% of agricultural streptomycin sulfate 3000 ~ 5000 times the liquid, 50% Daisen ammonium 600 times liquid, spray The drug should focus on the mildly ill and the surrounding plants. 3. Sclerotinia: At the beginning of the disease, 50% fast keratin 1500 times or 25% carbendazim 400 times, or 50% tarpaulin WP 500 times, spray once every 7 days, spray 2 to 3 times.