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Persistence of diflubenzuron on Appalachian forest leaves in stream water

Harrahy, E.A., Wimmer, M.J., Perry, S.A., Faber, D.C., Miracle, J.E., Perry, W.B.
Journal of agricultural and food chemistry 1993 v.41 no.11 pp. 2191-2196
diflubenzuron, insecticide residues, leaves, forest trees, streams, nontarget organisms, aquatic organisms, water pollution, adverse effects, West Virginia
The persistence of diflubenzuron on Appalachian forest leaves placed in stream water was examined using a new gas chromatographic/mass spectrometric method for analyzing the pesticide. Leaves came from trees aerially sprayed with Dimilin in the spring and left to weather during the growing season. The rain exposure minimizes loss of pesticide when the treated leaves are first immersed. After diflubenzuron coverage was measured, leaf samples were placed in a headwater stream and residual diflubenzuron was monitored as a function of time. During July and August, the amount of diflubenzuron on white oak decreased significantly (by 36% and 23%, respectively) within the first 48 h of stream incubation, reaching less than 10% of the original concentration within 3 weeks. In the December studies with yellow poplar, red maple, and white oak leaves, the rate of loss of diflubenzuron was slow. After 54 days in the stream, yellow poplar and red maple leaves retained 45% and 40%, respectively, of the original diflubenzuron and white oak showed no significant loss. In laboratory experiments mimicking the December field conditions, no significant loss of diflubenzuron was seen from yellow poplar leaves. In view of the persistence of diflubenzuron on hardwood leaves observed throughout the growing season to leaf fall, at low stream temperatures, nontarget aquatic organisms that consume these fallen leaves may be exposed to the pesticide for a significant period of time.