Since herbicide-resistant weeds have become the top priority for weed control over the past few years, it seems that most growers and commercial applicators are placing more emphasis on the quality of their herbicide application. There are several important components to a successful herbicide application, i.e., correct weed identification, matching the herbicide to the targeted weed species, proper spray nozzle selection, and accurate sprayer calibration. However, with the mix of crops common in Mississippi and the types of herbicides required to manage herbicide-resistant weeds, sprayer cleanout after the herbicide application is just as critical as the considerations prior to and during the herbicide treatment.
Unfortunately, not all herbicides are created equally when it comes to sprayer cleanout. Some herbicides, especially granular or dry flowable formulations, may settle out of solution and form residue in the bottom of the spray tank or get lodged in strainers. Others may adhere to the walls of the tank and/or hoses (especially in poly tanks or when hoses are worn).
Regardless of the herbicide used, there are three similar goals when cleaning a sprayer. These include diluting the active ingredient below damaging concentrations, deactivating the herbicide, or removing the herbicide from the spray system. For example, most glyphosate products can be purged from a sprayer by flushing an adequate amount of clean water through the system. Some commercial tank cleaners or chlorine bleach are effective for reacting with sulfonylurea herbicides (Classic, Permit, Resolve) and converting them into their inactive forms. Industrial strength ammonia can be useful for dislodging herbicide residue in tanks and hoses.