1. Large spot disease. Blotches first developed from the base leaves and gradually spread to the upper leaves. At the early stage of disease, water-soaked blue-grey patches appeared on the leaves and gradually expanded toward both ends to form yellow-brown shuttle-shaped or spindle-shaped large spots. Light growth was weak and grains were small, resulting in a reduction in yield. In severe cases, the whole plant died. The suitable temperature for the onset of large spot disease is 18 to 23°C, and the infection and spread of pathogens require higher humidity. During the growing season of maize, the climate with high humidity and low humidity is most conducive to the reproduction of pathogenic bacteria, and the epidemic of the disease is most likely to occur. Big spot disease occurs severely in cold areas.
The methods for controlling corn leaf spot include: 1 using resistant varieties; 2 using fungicides for high-value corn; 3 crop rotation and removing diseased bodies. The use of fungicides "New Star" to control large spot disease is more prominent, with a control effect of 98%.
2. Small spot disease. Maize leaf spot is one of the most important corn diseases. It is also a fungal disease. It occurs every year in the vast areas south of the Great Wall of China. The small spot causes the corn to produce a brown spot with a pale yellow to brownish edge, usually the lesion is ovoid, and its lateral expansion is limited by the veins. The occurrence of corn leaf spot needs a high warm and humid environment, and the temperature suitable for its onset is 20-32°C. Arid and sunny weather is not conducive to the epidemic of diseases.
The methods of controlling small spot disease mainly include: 1 using disease-resistant varieties; 2 using fungicides, this method is only applicable to high-value corn.
3. Sheath blight. Corn sheath blight is very serious in southern China. In the early stages of corn sheath blight, watery, gray-green, near-circular lesions appeared, and later became white, reddish to red-brown mottled patches. Humidity occurs when the humidity is high.
The prevention and control methods mainly include: 1removal of sick and disabled bodies, destruction or deep-deep burial; 2cultivation of disease-resistant varieties; 3 timely planting, increase of organic fertilizer, pay attention to drainage drainage, reduce field humidity, promote robust growth of corn, and improve disease resistance force. 4 chemical control, with 5% Jinggangmycin 1000 times, or 20% triazole copper EC 1000 times, or 50% carbendazim WP 500 to 800 times, spray control. When spraying, pay attention to the stem below the ear, in order to obtain better results. In the early stage of disease, removal of diseased leaves is the best measure to prevent further spread of the disease.
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