A system for assessing the distribution and incidence of tobacco viruses is given. Essentially, one in 1 × 105 plants in several areas of tobacco production in North Carolina comprises the sample and the data are extrapolated to the total crop to determine overall incidence. Virus incidence on tobacco in North Carolina was estimated from data obtained from 1977-79. Incidence on flue-cured tobacco for the three years was 1) tobacco mosaic virus 3.89, 5.60, and 8.48%, 2) potato virus Y 0.99, 0 54, and 1.65% and 3) tobacco etch virus 0 05, 0.17, and 0.68%. Incidence on burley tobacco was 1) tobacco vein mottling virus 3.19, 12.16, and 24.32% and 2) tobacco etch virus 0.09, 7.56, and 4.29%. Mixed infections and incidence of alfalfa mosaic, cucumber mosaic, peanut stunt, tobacco ringspot and tobacco streak viruses were less than 0.05%.

(Full article published with kind permission from "Tobacco International")