Symptoms are distributed in Shandong, Henan, Anhui, Liaoning, Heilongjiang, Yunnan, Guizhou, Fujian, Hunan, Hubei, Shaanxi, and Taiwan. The entire growth period can occur, and more fields occur. Infected leaves produce round or wavy necrotic markings. Most of them fade from green to yellow. The vascular bundles affect the transport of moisture and nutrients, resulting in dry leaves and reduced quality. Brown streaks or depressions can be seen on the stem or petiole.
Pathogen Tobacco ring spot virus referred to as TRSV, said tobacco ring spot virus, a virus. The virus particle is spherical and has a diameter of 29 nm. Passivation temperature 60 °C, dilution limit l0000 times, in vitro survival at room temperature for 4 days, a 18 °C conditions, the intimacy can be maintained for 22 months.
Transmission routes and disease conditions The source of the virus can be wintered on perennial Solanaceae, Cucurbitaceae, Leguminosae and other hosts. During the week, it is mainly transmitted through frictional contact with the juice. Viruses invade through wounds on the leaves and roots. Insects and nematodes can also spread the virus. Excessive nitrogen application in tobacco fields is prone to disease, and there are many nematodes in the soil or more wild host in the field.
Control methods (1) Use disease-free strains to keep seed. (2) Adopt formula fertilization technology to avoid partial application and over-application of nitrogen fertilizer. (3) Timely control of nematodes and insecticides. (4) Strengthen field management. Field operations should be preceded by healthy strains, pay attention to the removal of field wild hosts and reduce the source of poisons.
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