Further Researches on the Relationship between Aphid- avoiding and Tobacco Virus Disease Occurring

According to the anti- disease effects of manifold measures in tobacco seedbeds, the comparatively proper period and measures of aphid- avoiding to reduce tobacco leaf losing in term of virus are picked out. The result showed that the anti - disease effect of prevent worm netting with aperture 1/40 mm was the best, the effects of hanging plastic strips and tiling plastic membrane around seedbed were relatively good. When cultivated in netting, the ratio of virus- carrier tobacco seedling of comparison treatment was over 30%, but the ratio of above three measures was very low. When cultivated in fields, the anti- virus- disease effects of above three measures was prominent in course of 25 days after transplanting, but the effect of each treatment had no evident difference compared with comparison treatment 30 days or 40 days after transplanting. The anti- virus- disease effect of the treatment covered with netting was distinctly better than comparison treatment 45 days or 60 days after transplanting, so aphid - avoiding measures before tobacco seedling transplanting associate with plastic membrane covering after transplanting were essential for preventing and control of virus diseases.