Now that herbicides containing alternative herbicide sites (modes) of action are being mixed with glyphosate and a greater diversity of herbicide resistant crops are being grown, proper sprayer cleanout and knowing the type of herbicide resistant crop planted in a specific field is very important.
Sprayer cleanout is especially important before spraying extremely susceptible crops such as sugarbeet. Herbicides can become attached to sprayer parts, especially tanks and other parts made of plastic.
Growth regulator and ALS-inhibiting herbicides are the most likely herbicides to adhere to plastic material. After these herbicides become attached to the plastic they can be removed by herbicides and adjuvants used in future sprayer loads.
The worst-case scenario of herbicides adhering to plastic tanks and sprayer parts is when a mixture of a growth regulator herbicide is left in a sprayer tank overnight or for multiple days before being emptied.
To compound the problem if the next spray mixture has herbicides and adjuvants that act as tank cleaners and this spray mixture is left in the tank for multiple hours, the attached herbicide can be removed and becomes mixed with the current spray mixture.
For additional information about proper sprayer cleanout consult page 77 of the 2011 NDSU Weed Control Guide. This can also be found online by clicking here.