Influence of selected herbicides on the sensitivity of flue-cured tobacco to ozone

Two flue-cured tobacco cultivars NC 88 and Coker 319 were grown in a greenhouse. Four weeks after germination, the seedlings were transplanted into a soil:weblite:peat mix (1:1:1). Treatment with herbicide was as follows: Enide 50W at 3 oz/1000 sq ft, was diluted in water and applied to the base of each plant immediately after transplanting. Paarlan, at 2 pt/acre, was incorporated into soil mix one week before transplanting. Tillam, at 2 2/3 qt/acre, was incorporated into soil mix immediately before transplanting. Two weeks after transplanting, half of the plants in each treatment were fumigated with ozone, at 15 pphm/2.5 hr, on four successive days. One week later, the plants were harvested. Ozone injury was rated as percentage weather fleck for each plant. The excised plants were oven-dried at 75C for 48 hours, ground to pass a 20-mesh screen and analyzed for reducing sugar, total nonstructural carbohydrate and nicotine. Paarlan reduced ozone sensitivity more than Tillam yet both Paarlan and Tillman reduced ozone sensitivity of Coker 319 equally. Ozone fumigation reduced the reducing sugar content of NC 88 and Coker 319. Paarlan and Tillam treated NC 88 had more reducing sugar than nonherbicide-treated NC 88. Coker 319 had less reducing sugar more » and was more ozone sensitive than NC 88 under the conditions of this study. « less