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Persistence of diflubenzuron on Appalachian forest leaves after aerial application of Dimilin

Smith, R.R., Wellings, D.L., Toney, S.R., Faber, D.C., Miracle, J.E., Carnes, J.T., Rutherford, A.B.
Journal of agricultural and food chemistry 1993 v.41 no.11 pp. 2184-2190
diflubenzuron, insecticide residues, leaves, forest trees, aerial application, West Virginia
Using a new method for the analysis of diflubenzuron, the active ingredient in the pesticide Dimilin, the persistence of diflubenzuron on leaves of 20 Appalachian forest trees of 7 species was studied throughout the 1991 season after aerial application of the pesticide. Composites were made from leaf samples of each the upper and lower tree canopies, and replicate subsamples were analyzed for diflubenzuron concentration. The two values closely agreed, confirming composite homogeneity and precision of the analytical method. Growth dilution of diflubenzuron during this study was negligible. A significant loss of diflubenzuron from the foliage, ranging from 20% to 80%, was observed within the first 3 weeks after application. The remaining diflubenzuron was generally found to persist for the rest of the growing season until leaf fall, at which 13 of the 20 trees retained more than 20% of the original pesticide applied. The remaining seven trees, consisting of all five yellow poplars and two black oaks, showed from 5% to 20% diflubenzuron retention, primarily due to a greater initial crop. At leaf fall, the residual diflubenzuron is delivered along with the leaves to the streams and the ground litter underlying the canopy.