Sorghum leaf spot disease
The symptoms are also called scabs. All parts of the whole plant can be affected, mainly damage the leaves. The lesions are irregular in shape, long to spindle or semi-circular, ranging in size from about 1 cm in size, yellow-brown to gray-brown with red-purple edges. The lesions often start at the leaf margin or the tip of the leaf, and some also occur at the leaf surface or in the upper part of the spike, causing the flag leaf to collapse. The expansion of lesions often fused into larger plaques. Scattered or lined black granules were found on the dried leaves at the later stage, ie pathogenic conidia. Seed worms infected with similar symptoms. Beijing, Shanxi, Inner Mongolia, northeast, and southwest have all happened. The damage is getting worse.
Pathogen Phyllosticta sorghina Sacc. Called S. sorghum leaf spot fungus, belonging to the semi-known fungus subphylum fungi. Conidia are black, subglobose, scattered on leaf surface, prominent epidermis, size 64-194um. Conidia elliptic, unit cells, colorless, size 3.5-62.0-3.0 (um). In addition to infestation of sorghum, it can also infect alfalfa, millet, alfalfa, sugar cane, sudan grass and so on. Transmission routes and pathogenic conditions The pathogens overwinter on diseased bodies with conidia. In the following year, Beijing, Jilin and other places began to develop in June, and the symptoms were obvious or prevalent from July to August. It has been observed that the early cropping of the plots is worse than that of late sowing. There was a difference in disease resistance among the varieties. In the same plot, the incidence of resistance to No. 7 and Shenza No. 5 was heavier, while the resistance to No. 4 was not affected. In 1994, the hybrid sorghum Kang 7 and Shenza 5 planted in Miyun and Yanqing in Beijing were poorly resistant to the disease. Coupled with the special climate in that year, the drought in June was not rainy. After July, the rainfall increased, the rainfall was 575mm, and it was 268mm in August. , more than in previous calendar years, and the daily lighting was significantly reduced. From July to August, the air humidity was 78.7%-79%, and the temperature was 0.5-2.5°C higher than in previous years. This kind of humid and hot weather caused the leaf spot. The epidemic of the disease. In recent years, the disease has been on the rise, resulting in serious or absolutely no harvest.
Prevention and control methods (1) In response to local conditions, select disease-resistant varieties suitable for local cultivation. When introducing new varieties, attention should be paid to combine agronomic traits and disease resistance, and to select new varieties that are suitable for local high-quality, high-yield and disease-resistant varieties. (2) Suitable sowing should not be premature. (3) In the early stage of onset of disease, spraying 36% Thiophanate Suspension 600x or 50% Benomyl WP 1500x, 80% Penc WP 600x, 80% M-45 wettable powder 600 times, 30% green leaf Dan wettable powder 500-800 times liquid.
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