Sorghum leaf spot disease

The symptoms are also known as spot disease. The disease can occur in all parts of the plant, mainly harmful leaves. The plaque is irregular in shape, long to fusiform or semicircular in size, up to more than 1cm, yellowish brown to grayish brown, with reddish purple edges. The disease spot often starts at the edge or end of the leaf, and some occur on the leaf surface or the upper part of the ear, causing the flag leaf to fold. The expansion of the disease spot often fused into larger patches, and scattered or rows of small black spots could be seen on the dry leaf spots in the later stage, that is, the conidium of the pathogen. Seed glume infection produces similar symptoms. It occurred in Beijing, Shanxi, Inner Mongolia, Northeast and Southwest. The harm is becoming more and more serious. The pathogen Phyllosticta sorghina Sacc. It is called sorghum leaf spot mold, which belongs to the subphylum of semiknowns. Conidium black, subglobose, scattered on the leaf surface, protruding epidermis, the size of 64-194um. The conidia are oval, unicellular, colorless, 3.5 Mel 6 × 2.0 Mel 3.0 (um) in size. In addition to infecting sorghum, it can also infect millet, millet, paspalum, sugarcane, Sudan grass and so on. The pathogen of transmission and disease condition overwintered on the diseased body by conidia. In the following year, Beijing, Jilin and other places began to develop the disease in June, and the symptoms were obvious or epidemic from July to August. It is observed that the disease of early sowing field is more serious than that of late sowing field. There were differences in disease resistance among varieties. in the same field, the disease was more serious in Kang 7 and Shenza 5, but not in Kang 4. In 1994, Beijing Miyun and Yanqing planted hybrid sorghum Kang 7 and Shenza 5 with poor resistance to the disease. in addition, the climate of that year was special, there was no rain in June, the rainfall increased after July, and the rainfall 575mm reached 268mm in August, which was more than that of previous years, and the sunshine decreased obviously. From July to August, the air humidity was 78.7% Mel 79%, and the temperature was 0.5 ℃ higher than that of previous years. Caused the epidemic of leaf spot disease. In recent years, the damage of the disease has a rising trend, serious loss of production or harvest. Control methods (1) according to local conditions, select disease-resistant varieties suitable for local cultivation. When introducing new varieties, attention should be paid to combining agronomic characters with disease resistance to select new varieties with high quality, high yield and disease resistance which are suitable for the local area. (2) sowing at the right time should not be prematurely. (3) at the initial stage of the disease, 36% methyl thiophanate suspension or 50% carbendazim wettable powder 1500 times, 80% bengke wettable powder 600 times, 80% Dasheng M-45 wettable powder 600 times, 30% Lvyedan wettable powder 500 times 800 times.