Q: As a follow-up to my earlier problem, can you tell me more about how I should be cleaning my sprayer?
A: For the readers, let me give you the background story to this question. A field manager contacted me in late fall with a dieback problem with their ryegrass overseed on a bermudagrass field. The overseed looked healthy during germination and early in the fall. Then, late in the fall, a large streak across the field began to fade out after a bit of warm weather.
The field manager thought the warm weather resulted in the field drying out, so they increased the irrigation amount. The irrigation did not help, and within a few weeks of noticing the symptoms, the affected area had almost no living ryegrass. I made a brief inspection, and the pattern of dead turfgrass looked like whatever caused the problem came from a boom sprayer. The field manager indicated that since the ryegrass was seeded, they had only applied one spray application of a fertilizer at a low rate. Since that was not likely the cause, we next looked at his pesticide spray records.
The previous use of the sprayer was to apply a sufonylurea herbicide on bermudagrass. That information allowed us to deduce the cause of damage. Herbicide residue was still in the tank when the turf manager mixed and sprayed the fertilizer. It does not take much sufonylurea residue in the tank, boom lines, or pump to cause damage to ryegrass. The product is also slow to kill susceptible ryegrass when it is cool; but with warm weather, it became more efficacious. Although you may not experience any problems using only a water flush between applications of multiple products over the season, some product formulations leave residues and require a more thorough cleaning than just rinsing with water. If not removed, the residues may react with subsequent products or have direct negative consequences, as was the case here.
The label for most chemicals provides directions for cleaning spray equipment. Depending on the pesticide chemistry, the manufacturer may specify dilute ammonia, chlorine bleach, commercial cleaners, or household detergents be used for cleaning. Each has a specific purpose, and they should not be mixed together. For example, if ammonia is mixed with chlorine bleach it will produce a dangerous chlorine gas that can severely irritate eyes and lungs.
Tanks, hoses, pumps, strainers and screens may accumulate residues, so all parts of the sprayer system should be cleaned. The following is a recommended clean out procedure, but follow a chemical’s label if it specifies a different process:
1. Drain the sprayer immediately after the last load. Do not allow spray solution to remain in the tank or boom overnight. Thoroughly rinse the inside surface with clean water. Spray rinse water through the spray boom for at least five minutes.
2. Fill the sprayer tank with clean water and add the appropriate cleaning solution. Fill the boom and hoses, and allow the agitator to operate for 15 minutes.
3. For a few hard-to-remove chemicals, allow the sprayer to sit while full of cleaning solution for several hours (as directed) so that the chemical residue can be removed from inside the tank.
4. Spray the cleaning solution through the booms.
5. Remove the nozzles, screens and filters for cleaning with a soft brush and cleaning solution. Soaking these in cleaner may be necessary to remove some pesticide residues.
6. Rinse the sprayer to remove cleaning solution and spray rinse water through the booms.
7. Rinse the exterior of the entire spray system, including the boom, with clean water.[Note: Appropriately dispose of all rinse water at the field (target site) or on pad designed to capture the solution.]
When it comes to sprayer clean-out, it is better to be safe than sorry. The best source of information on how to clean the sprayer is the product label. Make sure to keep an assortment of cleaners on hand that match the label recommendations for the products used.
Grady Miller, Ph.D.
Professor and Extension Turf Specialist
North Carolina State University
Send them to Grady Miller at North Carolina State University, Box 7620, Raleigh, NC 27695-7620, or e-mail firstname.lastname@example.org
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