Melon leaf blight often occurs in the late and late stages of melon growth. It is a devastating and endemic disease that often causes a large number of dead leaves, seriously affecting yield and quality.
First, the symptoms
The leaves of melon leaf blight mainly damage the leaves, and the lesions are brown dots at the early stage of disease. They gradually expand into dark green circles with diameters of 2-5 mm. The edges are water-stained and slightly uplifted. The boundaries between diseased and healthy parts are distinct, with obvious ring patterns. . The center of the lesion is white, and the periphery is a chlorotic brown halo. Several lesions in the late stage of the disease can synthesize large plaques, causing leaf scorch. The bacteria can invade the fruit and form a fruit disease. The disease is similar to the symptoms of the leaves in the early stage and brownish disease in the later stage.
Second, the incidence of the law
Pathogens of melon leaf blight are Amphora spp. In addition to harming melon, it can also damage watermelon, cucumber, zucchini, and sponge gourd. The pathogens overwinter in the soil and in the unripe organic fertilizer with mycelium or conidia, and they can also winterize with the seed. Bacteria can also be infested in greenhouse melon crops in winter and become the primary source of infection in the following year. Conidia spread by air currents or flowing water. After the spores germinate, they infect the leaves. When the conditions are appropriate, the symptoms can be seen within 3-4 days, and a large number of conidia are quickly generated for reinfection. The temperature during the melon period is above 25°C. Continuous rain and timely rain are fine, and the field temperature is high, which is conducive to the occurrence of diseases. Heavy crops, heavy soils, large amount of nitrogen fertilizers, excessive density, and weak growing fields are heavy.
Third, control methods
1. Seed treatment: soaking in the sun before sowing, drying, soaking for 10-15 minutes with 0.1% potassium permanganate or 40% formaldehyde 100 times, soaking with water after soaking, so as not to affect the germination.
2. Strengthen field management: High-ridge film-covered cultivation techniques are adopted to prevent flooding of large floods. Water should be watered in the morning or evening when the weather is hot. Apply sufficient organic fertilizer and phosphorus and potassium fertilizers, and avoid using excessive nitrogen fertilizer. During the period of sitting on the cucumber, potassium dihydrogen phosphate or all kinds of trace fertilizers were sprayed to increase the disease resistance of the plants.
3. Chemical control: During the watering stage or before the rain, it can be used 75% chlorothalonil WP 800 times, or 1:1:200 Bordeaux spray to prevent disease; 75% chlorothalonil 600 times, or 70% mancozeb 500 times, or 50% acetaminophen 1500 times control. Spray every 6-8 days, spray 3-5 times.
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