Auxin-containing herbicides dicamba and 2,4-D have brought new control options to the field in the battle against glyphosate-resistant broadleaf weeds, however it’s important for growers using auxins to take precautions. Residue from the herbicide can be retained by certain types of applicator hoses and can injure sensitive crops.
According to recent research published in the journal Weed Science, depending on the amount of residue and the growth stage of the plant at the time of application, the impact on soybeans can range from cosmetic leaf injury to 80 percent yield loss.
The multiyear research project featured by the journal evaluated the amount of dicamba retained by five types of application hoses: PVC, polyethylene, polyurethane, PVC/polyurethane blends, and synthetic rubber. Researchers also explored whether cleaning sprayers with water alone or with water plus ammonia made a difference in the amount of dicamba residue each type of hose retained.
The PVC/polyurethane blend and synthetic rubber hoses were found to retain the most dicamba analyte – producing the greatest soybean injury and the greatest reductions in height, dry matter, and yield. The polyethylene hoses retained the least dicamba analyte. While cleaning the hoses decreased residues in all hose types, no differences were observed between adding ammonia to the cleanout solution versus using water alone.
Researchers say differences in the amount of dicamba analyte retained by various hose types may be attributable to the manufacturing process, the internal chemical composition of the hoses, and how quickly that composition breaks down. Scans conducted with electron microscopy showed there were imperfections in new PVC polyurethane and synthetic rubber hoses that could deplete the inner wall. The polyethylene blend hoses were smooth and free of imperfections.
“The findings produced by the study can be especially helpful to producers who use a single sprayer to treat multiple crops and transgenic traits,” says research team member Daniel B. Reynolds, Ph.D., of Mississippi State University. “Using polyethylene hoses may help to ensure a more thorough cleanout of dicamba before treating sensitive crops.”