(1) Harmful symptoms: Cotyledons and true leaves initially produce irregular, small-shaped gray-green lesions that gradually lose their moisture and appear pale. Later, the lesion gradually expands to form an irregularly shaped large spot with brown spots around the lesion, a pale halo around the periphery, a brown center, and a dark black ring pattern. There is a layer of black mold on the lesions, which are the conidial stems and conidia of the germs. In severe cases, lesions occupy the majority of the leaves and finally die. The black ear rots after the damage.
(2) Pathogen and Pathogenesis: Ramie black spot is caused by fungi. The conidial stems of the bacteria are solitary or tufted, dark brown, with 1 to 3 geniculate bends and multiple septa. Conidiophores have horizontal and vertical divisions, contracted at the divisions, have long beaks, dark brown. The pathogens overwinter on sick leaves and seeds and infect young seedlings in the coming year. New conidia are produced on the diseased plants to spread wind and rain. The lower debilitating leaves are susceptible to disease. Wet and wet years have become more severe.
(3) Control methods: 1 Use disease-free seeds or seed dressing with 0.4% 50% carbendazim WP. 2 Immediately after harvest, the sick leaves are burned or buried deeply, and deeply plowed and deep plowed. 3 During the onset of the growing period, spray the medicine. There are 50% carbendazim WP 800 times or 50% thiophanate-methyl WP 1000 times.
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