Hose Types and Dicamba (York)
In the Auxin Herbicides – Best Management Practices training we presented across the state this spring, one of the things we talked about was sprayer cleanout. I mentioned that some research conducted at Mississippi State showed that the material the hose was made of impacted how much dicamba was retained in the hose, or hose composition could impact how easily dicamba can be removed. Apparently a few folks were paying enough attention to remember that and now I am getting follow-up questions.
That research has recently been published (Cundiff, Reynolds, Mueller. 2017. Evaluation of dicamba persistence among various agricultural hose types and cleanout procedures using soybean as a bio-indicator. Weed Science 65:305-316).
The researchers used 10-ft sections of five different hoses. They filled the hoses with Engenia and Roundup Weathermax at concentrations typical of use rates on Xtend-traited crops. They let the spray solution remain in the hoses for 48 hours. The hoses were then drained and refilled with water only or a 1% ammonium-water mixture. The cleanout solution remained in the hoses for 24 hours and was then discarded. The hoses sat empty for 48 hours and were then filled with a Roundup solution typical of field use rates. That Roundup solution remained in the hoses for 48 hours and was then sprayed on soybeans.
Data in Table 1 below are averaged over four runs of the experiment. There are three things to note. First, either the water or ammonia cleanout reduced soybean injury compared to no cleanout solution. Second, soybean injury was similar with the water and ammonia cleanout solutions. Third, hose composition made a big difference. The hose made of the low density polyethylene blend retained the least amount of dicamba in the absence of a cleanout solution. And, there was no soybean injury following cleanout of that hose versus varying amounts of injury following cleanout of hoses of other compositions.
The researchers concluded the following: “These data may be helpful to producers who wish to use a single sprayer with multiple crops and crops with transgenic traits. These data would suggest that a polyethylene hose may facilitate a more thorough cleanout of dicamba before re-using the sprayer on sensitive crops.”
Please note that this experiment and the procedures used were specifically designed to compare hose types. The cleanout procedure was not the triple rinse recommended on the labels of dicamba products registered for Xtend-traited crops. The intent was not to document whether dicamba can be cleaned from a sprayer; the intent was to compare hose materials.