Effects of Timing of Oust Application on Survival of Hardwood Seedlings

Abstract Oust herbicide (sulfometuron methyl) was applied with or without surfactant at the rate of 2 oz/ac in early July, early August, early September, and early October to black cherry, red maple, and white ash seedlings of three sizes to evaluate their tolerance to Oust. Treatment plots were in northwestern and central Pennsylvania. Survival and damage of treated seedlings were compared with a no-herbicide control 1 year after treatment. Black cherry and white ash were sensitive to Oust; red maple showed little sensitivity. Greatest damage and mortality to black cherry occurred with early July applications of Oust; applications from early August onward resulted in greater black cherry seedling survival and less severe damage than July applications. White ash mortality was high with applications from early July through early September. Early October application of Oust resulted in the least mortality of white ash. Adding surfactant to Oust significantly increased damage and mortality of black cherry and white ash. North. J. Appl. For. 9(1):22-27.