Clean out those tanks! With the postemergence application of pesticides approaching, it is important to properly clean spray tanks.

Without proper clean out of sprayers, herbicide residues from one spray load can contaminate the next load and damage a sensitive crop. Postemergence sprays are making direct foliar contact with the crop and are not being diluted with soil as with preemergence application, notes Chris Boerboom, University of Wisconsin Extension weed scientist.

Recommended procedures or steps to properly clean out a sprayer following herbicide application are listed on the pesticide label. Some labels will indicate that the cleaning solution stay in the sprayer for several hours to overnight.

Boerboom listed the following general guidelines for cleaning spray tanks in the May 22 issue of the Wisconsin Crop Manager.

• Flush the sprayer tank, lines, and booms thoroughly with clean water and apply the pesticide-contaminated rinsate to labeled sites.
• Fill the sprayer to capacity with water, adding 1 cup of trisodium phosphate or household ammonia for each 10 gallons of water. If neither is available, use a strong detergent or soap. Hormone-type herbicides (2,4-D, dicamba, etc.) are best removed with ammonia.
• Wash the tank and pump parts thoroughly by running the sprayer for about 5 minutes with the flow to the nozzles turned off.
• If possible, let the cleaning solution stand in the sprayer overnight. Remember, household ammonia will corrode aluminum sprayer parts.
• Discharge the liquid from the tank, spraying some through the nozzles.
• Drain the sprayer completely and remove nozzles, screens, and strainers.
• Scrub all accessible parts with a stiff bristle brush.
• Rinse the sprayer thoroughly with clean water and reassemble.