Sulfonylurea Herbicides Sprayer Cleanout Fact Sheet


Fred Degiorgio
Gabrielle King
(303) 716-3909
(302) 992-6285

Key Summary Point:

  • Proper cleaning and maintenance of spray equipment are essential parts of effective pest control.
  • Sulfonylurea herbicides are no more difficult to remove from application equipment than any other herbicide. As with any herbicide, if a highly sensitive crop is going to be sprayed, it is important to use thoroughly cleaned equipment. When a crop is highly sensitive to any herbicide, even a very low level of carry-over can cause damage.
  • Many factors can influence the effectiveness of sprayer cleaning procedures, including design and maintenance of the equipment, residues from previous applications, and presence of tank mix partners (including additives).

       Because residues from previous applications can trap subsequent compounds and make it more difficult to clean them from the system, it is important to start with clean equipment. Equipment should be rinsed immediately after spraying, using cleaning procedures specified on the label as soon as possible after rinsing so that compounds will not dry onto the surface of tanks and hoses.

       The product label also notes approved product combinations. Incompatibility between products can result in deposits that are difficult to clean from equipment. For approved product combinations, it is important to add the products in the recommended order. Adding products in the wrong order can also result in deposits that are difficult to remove.

       Even when the sprayer is operated until visibly empty, small amounts of spray solution can remain in the equipment. When the same equipment is used to spray different crops during the season, injury to sensitive crops may result if traces of previous products remain in the sprayer. The sensitivity of various crops to injury by different products is highly dependent on the specific product, the rate at which it is applied, the ability of the vegetation to break down the product, and the growth stage of the vegetation.

       Cleanup procedures work through three primary mechanisms: dilution, deactivation, and extraction. All procedures use dilution, which lowers the concentration of the crop protection product by repeated addition and drainage of fresh cleaning solution. Deactivation occurs when the cleaning solution causes the crop protection product to decompose into compounds that are no longer active for their intended use. Extraction occurs when the cleaning solution causes chemical deposits that can accumulate in application equipment to loosen or dissolve.

       Older, poorly maintained spraying equipment with rusted, pitted components can trap crop protection products, making them difficult to remove. Multiple applications of a product over a period of time without interim rinsing can lead to a buildup of deposits. Certain tank mixes can hinder cleanup by forming deposits and trapping products on equipment surfaces. If the sprayer is not clean prior to using, deposits from a previously used product can also trap subsequent products and ultimately reduce their exposure to the cleaning agent. These deposits can break free during subsequent applications.

       When proper cleanup procedures are not followed, crop protection products left in the spray system can damage sensitive crops in a future application. Adequate cleanup procedures should be followed, according to the product label. DuPont works with sprayer manufacturers to design equipment that can be efficiently cleaned. DuPont also conducts research on improving cleanout procedures and on evaluating the effectiveness of cleaning agents.