Abstract: There are 6 species of aphid flying and migrating to tobacco plants in the region of cultured tobacco in the north of Wei River, Shaanxi Province, but only Myzus persicae (Sulzer) can do damage to tobacco. Tobacco plants are divided into grade 0, I, II, III and IV according to the aphid quantity per plant in the period of its serious damage, and leaf area polluted by mould caused by honey dew secreted by the aphid in the period of tobacco ripening. Compared with grade 0 not injured by the aphid, the mid-and high-grade tobacco leaves in grade I,II,III and IV injured by the aphid are reduced by 6.93%, 13.05%, 28.51% and 30.94% respectively. The economic losses caused by the aphid are 9.86%, 23.81%, 36.12% and 39.59% respectively. The analyses of chemical composition indicate that nicotine of the leaves in grade I,II, III and IV is reduced by 10.61%, 19.29%, 10.61% and 25.40%, reducing sugar is reduced by 15.04%, 19.23%, 40.78% and 44.86%, and protein are increased by 16.17%, 31.77%, 37.02% and 38.72% respectively. These show that both the external and internal qualities of the flue-cured tobacco leaves are influenced by the aphid injury. The economic loss of one aphid is about 0.0695%.

Key words: Myzus persicae (Sulzer)——flue-cured tobacco——economic loss ——quality