Lettuce brown spot is a fungal disease that is caused by the infection of the fungus Cercospora lentivius or Cercospora maculata of the subgenus genus Demenomyces, and mainly damages the leaves. The lesions on the leaves showed two symptoms. One was watery stains at the early stage of disease. Afterwards, it gradually expanded to a circular to irregular shape. Brown to dark gray lesions appeared with a diameter of 2 to 10 mm; the other was deep. Brown spots, irregular edges, waterspot-like halo around the periphery. When the environmental humidity is high, dark gray moldy material appears on the lesions, and the lesions merge with each other when severe, causing the leaves to become brown and dry. The first brown spot symptom was caused by the lettuce, Cercospora maculosa, and the C. verticillatum banana caused the second brown spot symptom. The pathogenic bacteria overwintered with mycelia and conidium plexus on diseased bodies. They were initially infested and re-infested with conidia, and spread by airflow and rain splash. In the case of continuous cloudy rain and snow, poor plant growth, or partial application of nitrogenous fertilizers, the disease will worsen. The main control methods: 1. Clean the countryside and promptly bring the diseased body out of the park and burn it. 2. Reasonable fertilization. The use of formula fertilization technology, increase organic fertilizer and phosphorus, potassium fertilizer, to avoid partial nitrogen fertilizer, so that plants grow robustly, enhance disease resistance. 3. Chemical control. At the beginning of the disease, 40% polysulfide suspension can be sprayed 500 times, or 75% chlorothalonil wettable powder 1000 times, 70% thiophanate-methyl wettable powder 1000 times, or 50% acetaminophen wettable powder 1200. ~1500 times liquid, or 60% ethyl aluminum phosphine wettable powder 500 times, etc., spray once every 10 days, continuous control of 2 or 3 times. Stop the medication 5 to 7 days before harvesting. Rushan Jinguo Food Co., Ltd , https://www.jinguofood.cn