Corn gray spot disease, also known as leaf spot disease, corn leaf spot disease, in recent years, the incidence of an upward trend, a serious threat.
Symptoms:
The main damage leaves. The lesions were elliptical to oblong in shape at the onset of the disease, with no obvious edges, gray to light brown lesions, and later brown. More lesions are limited to parallel veins, size (4-20) mm * (2-5) mm. When the humidity is high, gray moldy material grows on the back of the lesion.
Disease characteristics:
The disease is caused by a fungus, and the pathogenic bacteria are the semi-known fungi S. cerevisiae C. zeae and C. sinensis. The pathogenic bacteria overwintered with the diseased body and was the primary infestation source for repeated infestation. The rainy year in July-August is prone to disease, and individual plots can cause a lot of dry leaves. Pathogens can safely overwinter on sick bodies under dry conditions, but the sick bodies under the moist surface cannot overwinter. The topography and planting form have a great influence on its occurrence, and the sowing date, planting density, topography and fertilizer have little effect on corn gray spot disease.
Control methods:
1. Agricultural control: select varieties with better resistance to gray spot disease; reduce the initial infestation source in the fields through the autumn fall spring; use intercropping to improve the field microclimate and reduce the relative humidity in the field so as to achieve disease control The occurrence and prevalence of the epidemic should be controlled by the use of chemical control. The prevention of disease can also effectively reduce the number of pathogenic bacteria in the later winter. Immediately remove the diseased body after harvest. A large area of ​​rotation. Strengthen field management, timely drainage after rain, and prevent moisture retention.
2. Chemical control: spraying at the early stage of the disease, commonly used agents can be used 75% chlorothalonil WP 500 times, 50% carbendazim WP 600 times, 40% gram granules EC 800-900 times, 50 % Benomyl WP 1500 times, 25% Benzophenone EC 800 times, 20% Triadimefone EC 1000 times.
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