One, corn spot
1. Symptoms:
Maize big spot mainly damages the leaves of corn. When it is serious, it also damages the leaf sheath and temporal lobe. It starts from the lower leaves of the plant and then spreads upward. The lesions are long spindle-shaped, gray-brown or tan-colored, 5-10 cm long and 1 cm wide. Some lesions are larger, and the leaves are coked when severe. When the weather is wet, there may be dense gray mold layer on the lesions. In addition, there is a lesion that occurs on disease-resistant varieties, extending along the veins, with brown necrotic streaks, which generally spread slowly. Summer corn is generally more severe than spring corn.
2. The law of onset:
Pathogens are overwintering on field residual diseased plants (both mycelia and conidia) and are the primary source of infection for the second year of onset. The onset temperature is 20-28°C. When the conditions are appropriate, the germs reproduce rapidly, producing a large number of conidia, spread by the wind. The prevalence of the disease is mainly determined by the environmental conditions (rain, humidity), except for the susceptibility of the maize variety.
3. Control measures:
1 Select disease resistant varieties;
2 reasonably dense planting, increase organic fertilizer and phosphorus, potash;
3 At the beginning of the disease, 500% of 50% wettable carbendazim or 800-1000 times of 50% thiobacillus, or 800-1000 times of 80% thiophanate-methyl, or 800-1000 times of 80% thiophanate-methyl Liquid, 50-75 kilograms of liquid per acre, spraying once every 7-10 days, a total of 2 or 3 times.
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