The effect of mineral oil treatment in Burley 21 tobacco field on the control of potato virus Y(PVY-VN) mostly transmitted by green peach apid(Myzus persicae Sulzer) in nature was studied and the virus infection in some plants including potato, pepper, bramble, radish, etc near the tobacco fields as a virus infection source was tested by capillary tube precipitatioin test with PVY-antibody and bioassay in Xanthi-nc tobacco. The main source of PVY-VN infection in tobacco field in korea was potato(ca. 40% of test plants infected). Pepper and bramble were also infected by PVY-VN. The control level of PVY-VN infection by treatment of 0.75% liquid mineral oil with 3 % nonionic emulsifier to the plants was 84.8 % in case of the artificial transfection with a infected apterous aphid in laboratory. However, the reduction of PVY-VN disease severity in tobacco fields treated with mineral oil at late June was only 35.5%. These results suggest that mineral oil treatment is not so effective for the protection of aphid-born virus(PVY - VN) infection in tobacco fields.