Play it Safe: Clean Your Sprayer Equipment Before and After Each Use

It’s been quite the growing season across the state—in the west and north, it's been rain, hot temperatures, field flooding, high humidity, and more rain.  The south central and southeast have been hot and dry for some time. For most of you, the crop is finally catching up with the season, the plants are growing, and the planters are (hopefully) put away. Next on the list is the pesticide applications – fungicides, insecticides, and herbicides. All have short application windows, plus we have no control over the weather. With everything you have invested in this spring and early summer – time, money, equipment maintenance/repairs, and lost sleep – it would be a shame now to lose the crop, especially to something as avoidable as herbicide damage from pesticide residues left in the sprayer. Remember, now is not the time to cut corners – herbicides can damage susceptible crops when applicators do not thoroughly clean sprayer equipment before and after spraying different crops.

A quick post-application in-field rinse may not be enough. Even very small amounts of herbicide residue left in tanks, hoses, screens, fittings, or booms can seriously damage crops. Some herbicide products still call for applying pints or quarts per acre, but many now have application rates measured in ounces per acre. Residues from products at these lower application rates can affect crops even when trace amounts remain in the application equipment. For example, in the below image (Figure 1), a small amount of herbicide mixture containing dicamba left in the sprayer, was enough to cause leaf cupping and distortion symptoms on the next field of soybeans. 

Cleanout also matters when moving into fungicide season. With tar spot confirmed in the state and important fungicide decisions to be made, this is a good time to double-check your spray tank cleanout directions for each product before making the next pass. Fungicides may not cause the same crop-injury issues as herbicides, but these applications are often tank-mixed with insecticides, foliar and biological products, and adjuvants that can create compatibility problems, along with crop damage from herbicide residue if the sprayer is not properly cleaned.

Adjuvants can also complicate the situation.  Adjuvants, surfactants, and crop oils may dislodge old herbicide residues embedded in tank walls or hoses or help break down particles in screens. When they do, the adjuvants may cause an old, unwanted herbicide residue to mix into the spray liquid. If the next sprayer load is Roundup or Liberty herbicide, the surfactants in those products can act as a powerful tank cleaner, reacting with plant-growth regulator residues and causing unintended crop injury. Finally, many labels require the cleaning of sprayers before and after mixing and applying. Products with a label stating that the sprayer and equipment must be clean before mixing and loading, meaning you must thoroughly clean the spray tank and all lines and filters, following the label directions for the previously applied pesticide, prior to mixing the product. Remember, the label is the law.

Below are steps for the sprayer cleanout procedure that are listed on a dicamba herbicide label. It is a good idea to keep records of cleanouts, particularly with products that tend to stick to inside surfaces, such as oil-based formulations or auxin (Group 4) herbicides.  Always read and follow all label guidelines of the specific product(s) you are applying. Do not clean sprayers near desirable vegetation that may come in contact with rinsate, wells or other water sources. Also, don't forget to wear the proper personal protective equipment (PPE) as stated on the product label!

1. After spraying, drain the sprayer (including boom and lines) immediately. Do not allow the spray solution to remain in the spray boom lines overnight prior to flushing.
2. Flush tank, hoses, boom and nozzles with clean water. If equipped, open boom ends and flush.
3. Inspect and clean all strainers, screens and filters.
4. Prepare a cleaning solution with a commercial detergent or sprayer cleaner or ammonia according to the label directions.
5. Take care to wash all parts of the tank, including the inside top surface. Start agitation in the sprayer and thoroughly recirculate the cleaning solution for at least 15 minutes. All visible deposits must be removed from the spraying system.
6. Flush hoses, spray lines and nozzles for at least 1 minute with the cleaning solution.
7. Remove nozzles, screens and strainers and clean separately in the cleaning solution after completing the above procedures.
8. Drain pump, filter, sump and lines.
9. Rinse the complete spraying system with clean water.
10. Clean and wash off the outside of the entire sprayer and boom.
11. All rinse water must be disposed of in compliance with local, state, and federal requirements.

The below image (Figure 2) shows an example of sprayer contamination injury in a soybean field. In this field, pressure to keep the sprayer moving in the face of rain on the way resulted in damage to a soybean field. The herbicide contamination came from a tank-mix of mesotrione and nicosulfuron herbicides left over in the sprayer from a preceding corn field. The applicator thought everything had been thoroughly cleaned, but the below bleaching symptoms suggest the sprayer was not cleaned out completely.

Whether you are applying insecticides, fungicides or herbicides, application timing is always crucial. With a long to-do list and little time to spare, please do not gamble and only partially clean sprayers in order to save time and cover more acres. Your time-saving methods may be very costly in the end.