Lettuce leaf spot showed two symptoms: one was watery, and then gradually expanded to a round to irregular, brown to dark gray lesions; the other was a dark brown spot, irregular edges, peripheral Water stained halo. When wet, the dark gray moldy surface appeared on the surface, and the lesions merged when severe, causing the leaves to become brown and dry. Spread by air currents and rain splashes. In general, rainy or dew-light weather is favorable for disease. Plant growth or over-exposure to nitrogenous fertilizers will aggravate the disease.
Control methods: 1 Note removal of diseased leaves and diseased bodies, brought out of the field burned. And spray the tree general to disinfect and sterilize. 2 Qinggou drainage, to avoid partial nitrogen fertilizer, timely spraying plant stems can be thick, thick leaves, fresh leaves, plants flourishing, natural taste. At the same time, it can increase the ability to resist disasters, reduce the amount of pesticides and fertilizers, and reduce the residual poisons. 3 at the beginning of onset of spraying 40% polysulfide suspension 500 times, or 75% chlorothalonil wettable powder 1000 times plus 70% thiophanate-methyl WP 1000 times plus new high-fat film 600-800 times, Every 10 to 15 days rotation once, continuous control 1 to 2 times.