Avoiding crop injury due to contamination
Crop injury due to contaminated sprayers is becoming an ever-increasing problem in Montana. This problem can be avoided by ensuring that sprayers are properly cleaned between tank loads. When determining the correct clean-out procedure, it is important to consider the product' s mode of action, carrier, and additives. They all have an impact on what cleaning solutions to use and potential damage to sensitive crops.
Clean the sprayer in an area that will not contaminate water supplies, streams, or crops and in an area inaccessible to children, pets, and livestock. Pay particular attention to sensitive vegetation that is in the runoff area. The best method for rinsate disposal is in the field and in a manner consistent with the product' s label. The easiest way to do this is to have rinse water available in the field, either on the sprayer or support vehicle.
A tank-cleaning agent is designed to penetrate, loosen, and dissolve pesticide residues and then to remove them with the rinse water. In some cases, the agent will provide deactivation or decomposition of the herbicide.
Surfactants and fertilizer additives
- Commercial tank cleaners are recommended on many product labels and help remove water and oil soluble herbicides.
- Household ammonia, a commonly recommended cleaning agent, is effective at penetrating and loosening deposits and residues in the spraying system. Although ammonia does not decompose herbicides, it increases the solubility of some herbicides by raising the pH.
- Chlorine bleach can decompose residues of most sulfonylurea and other herbicides into inactive compounds. However, some tank-mix partners may inhibit the decomposition. Care must be used with chlorine bleach. Chlorine bleach can combine with fertilizers containing ammonia to produce dangerous chlorine gas, which is irritating to the eyes, nose, throat, and lungs. Also, rinsate containing chlorine bleach is not labeled for application to cropland.
- Kerosene or fuel oil should be used to remove oil-based herbicide formulations such as 2,4-D esters. Following the oil rinse, the system should be cleaned with detergent or ammonia. Use 4 gallons of kerosene with 1 pound of powdered detergent per 100 gallons of water.
When switching from a growth regulator herbicide (2,4-D, Banvel, or Stinger) to another postemergence application in broadleaf crops , special care should be taken if the following application involves surfactants or fertilizer additives. Such materials are particularly adept at removing previous herbicide residues from poly tanks, hoses and strainers and onto sensitive crops. It is recommended that a small amount of fertilizer or crop oil be flushed through the system before the application.
General cleaning guidelines
To avoid drying and hardening of pesticide residues, and potential corrosion and damage to equipment, clean the sprayer immediately following an application. If you are continuing with the same pesticide the next day, flushing with water is sufficient. However, if you are switching products or crops, a more thorough cleaning is required. Be sure to clean the entire sprayer system, not just the tank. Operate the pump and flush the cleaning solution through all hoses, strainers, screens, nozzles, and the boom. Small amounts of residue left in these areas can be sufficient to cause serious damage to a sensitive crop. Most injury occurs when switching between crops. The following procedure is recommended when there are no specific cleaning requirements given on the label.
1. Drain the sprayer tank and lines and rinse tank, boom, and lines with water for a minimum of 5 minutes.
2. Fill the tank with clean water and one of the following cleaning solutions per 100 gallons of water:
- 1 gallon household ammonia
- 8 pounds trisodium phosphate cleaner detergent
- commercial tank cleaner (follow instructions)
Flush the solutions through the entire sprayer system. For growth regulator herbicides, let the solution stand overnight. Add more water to fill tank and agitate solution for at least 15 minutes and flush through the nozzles. Drain the tank.
3. Remove the nozzles, screens, and strainers and clean them separately in a bucket of cleaning agent and water.
4. Rinse the entire system with clean water.
Consult the label
This publication provides general guidelines for cleaning your sprayer, but it is important to remember that the best source of information is the pesticide label. Consult labels for the products that were previously in the tank, and for the products that will be used for the next application.
Adapted from materials provided by the University of Missouri and Iowa State University.