Herbicide runoff study published in Forest Science

A recent issue of Forest Science includes an article by M.A. McBroom and others titled “Runoff of silvicultural herbicides applied using best management practices.” The authors are affiliated with Stephen F. Austin State University and NCASI. Results indicate that the best management practices applied in the study watersheds were very effective in controlling herbicide runoff and protecting aquatic ecosystems. The abstract follows.

“Nine small (2.2–2.9 ha) and four large (70–135 ha) watersheds in East Texas, USA, were instrumented to compare herbicide runoff under different silvicultural systems with best management practices (BMPs). Two treatments were evaluated: conventional, with clearcutting, aerial herbicide site preparation, and hand-applied banded herbaceous release; and intensive, in which subsoiling, aerial fertilization, and a 2nd-year aerial herbicide application were added. Herbicides were applied as operational tank mixes. The highest imazapyr concentration found in stream water was 39 μg L-1 during the first storm after application (23 days after treatment [DAT]) and in-stream concentrations during runoff events dropped to <1 μg L-1 in all streams by 150 DAT. The highest hexazinone concentration was 8 μg L-1 for the banded application and 35 μg L-1 for the broadcast application the following year and fell to <1 μg L-1 in all streams by 140 DAT. The highest sulfometuron methyl concentration found during a runoff event was 4 μg L-1and fell to <1 μg L-1 streams by 80 DAT. Approximately 1–2% of applied imazapyr and <1% of hexazinone and sulfometuron methyl were measured in storm runoff. Herbicide was found in streams during storm events only (all herbicides were <1 μg L-1 in all true baseflow samples), and peak concentrations during runoff events persisted for relatively short times (<24 h). These results suggest that silvicultural herbicide applications implemented with contemporary BMPs are unlikely to result in chronic exposure of aquatic biota; therefore, herbicide use under these conditions is unlikely to degrade surface waters.”  

Contact information 

Reference 

McBroom, M.W., J. Louch, R.S. Beasley, M. Chang, and G. Ice. Runoff of silvicultural herbicides applied using best management practices. Forest Science 59(2): 197-210.