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Symptoms occur in all areas. Mainly injure the leaves of cannabis, with primary dark brown dots, and then expanded into nearly round to irregular lesions, with a size of 2-10 mm, a central light brown, and a pale yellow color. The diseased leaves were covered with large and small lesions, resulting in dry leaves and early fall, the back of the lesions black fungus layer, the pathogenic bacteria conidiophores and conidia.
The pathogen, Cercospora cannabina Wakefeiid, is known as the Clostridium spp. The fruiting body is born on the back of the leaf and has no pedestal; the conidiophore stems are 2-10 bunches, light brown, uniform in color, upright and upright, a few with 1-2 geniculate ganglions, narrow apically, unbranched , Round to nearly truncated, with marked scarring, 0-4 diaphragms, size 16-673.5-5 (μm). Conidia whip, colorless, transparent, straight or slightly curved, base truncate or truncate, sepals 2) 1 ..., size 45-803-4 (μm).
Transmission routes and pathogenic conditions The pathogenic bacteria used for the wintering of mycelia or conidia on the diseased body became the source of infestation at the beginning of the year. After the onset of disease, the diseased part of the plant can continue to produce conidia and spread through the air flow for repeated infections. The fungus is a weak parasite, and the management of Ma Tian can't keep up, the growth and development of the hemp strains are easy to develop, and the incidence of disease is too low.
Control methods (1) Proper close planting, scientific fertilization, pay attention to the combination of nitrogen, phosphorus and potassium to enhance the resistance of plants. (2) Strengthen management, improve the ventilation and light transmission conditions in Ma Tian, and drain water in time after rain to prevent moisture retention, which can reduce the incidence. (3) At the beginning of the disease, spraying 1:0.5-1:100 sale of Bordeaux mixture or 50% diclofen copper (DT) wettable powder 500 times, 60% more Fortune mixture 600-800 times, 36% A Thiophanate-containing suspension 500 times, 50% benomyl WP 1500 times, 65% Tamycin WP 1000 times.
