Forest Herbicide Washoff From Foliar Applications
Field and laboratory experiments were conducted to develop and test methods for determining washoff of foliar applied herbicides typically used in forestry in the South.
Preliminary results show good agreement between results of laboratory methods used and observations from field experiments on actual precipitation events. Methods included application of known amounts of herbicide to individual leaves both in the field and in the laboratory. Washoff was determined by analysis of water runoff collected from individual leaves in the field following actual precipitation events, and from similarly collected water runoff from simulated precipitation events in the laboratory. Laboratory and field determinations of percent washoff of applied herbicide are in good agreement. As few as 10 drops of precipitation impacting a single leaf can wash as much 30% of applied herbicide off, and 3 mm of precipitation can wash as much as 100% of applied herbicide off foliage depending on elapsed time following application.