Publication 360, Fruit Production Recommendations: Filling and Agitation

Table of Contents

1. Tank water
2. Agitation
3. Filling the tank
4. Other Information on Pesticide Application
   • Handling and Mixing Pesticides
   • Filling and Agitation
   • Calculating Water Volume and Pesticide Rates
   • Sprayer Calibration and Nozzle Maintenance
   • Calculating Output
   • New Developments in Spraying Technology
   • Other Resources in Application Technology
5. Related Links

Filling and Agitation

Tank water

• Mix pesticides with clean water that does not contain debris, sand, mud or organic matter.
• Never let the water intake screen rest on a pond bottom when filling a sprayer.
• The water intake line near the screen must, by law, have a check valve or anti-backflow device. This prevents water-source contamination when the pump is shut off.
• Do not use a tank-refilling nozzle, volume-booster nozzle, or injection pump when refilling sprayer tanks from ponds or streams. These tank-refilling aids may contaminate the water source.
• When using a farm water supply, install a frost-free water hydrant outside the building. Place an anti-backflow valve or siphon prevention on the discharge end of the hydrant.
• If required, adjust the pH or hardness of the water before mixing spray materials in the tank. Where water is known to have an excessive salt content, compatibility of the water and the chemical at field strength should be tested first on a small scale.
  

Agitation

Agricultural products are formulated to be as emulsifiable as possible, but many do not mix well in water. They contain elements that do not dissolve (e.g. wettable powders), or they may be petroleum distillates (e.g. emulsifiable concentrates). Other products are heavier than water and form precipitates (e.g. fertilizers and powdered metals). Consequently, good agitation is very important.

Effective agitation requires water to "sweep" the bottom of the tank so that any precipitated material is picked up and re-mixed. Turbulence is not enough. If there is too little agitation, the pesticide will be applied unevenly. If there is too much agitation the pesticide may foam or cause an invert emulsion (forming a gel). There are two common types of agitation: mechanical and hydraulic.

Mechanical agitation is produced by paddles that are attached to a shaft mounted near the bottom of the spray tank. While relatively effective, this system cannot always sweep the very bottom of the tank, so there is always some material that precipitates out of reach.

Hydraulic agitation is accomplished by returning a portion of the pump output to the tank. Cylindrical and oval tanks are the ideal configuration for the rinsing (i.e. sparging) type of hydraulic return agitation system. This system consists of a tube located longitudinally along the wall of the tank, with volume booster nozzles aimed at that centerline so they sweep across the bottom. Volume booster nozzles take a small amount of water pumped into their venturi chamber and create a vacuum that draws three to four times that volume from the surrounding water and expels it out the end. For hydraulic agitation to be effective, the agitator nozzle(s) should be fed by a dedicated line from the pressure side of the pump (not the pressure regulator). They should have a valve to throttle the flow or completely shut it off to prevent foaming.

Filling the tank

Pesticide labels usually provide mixing directions for registered tank-mixes, often describing the order of mixing. Consult the package labels for information on the compatibility of different products. When the label does not provide mixing instructions for a registered tank-mix, pesticides should generally be mixed using the following procedure:

1. Fill the spray tank with water to half of the total spray volume required and start agitation. Add the different formulation types in the order listed below, allowing time for complete mixing and disper-sion after adding each product.
   • dissolvable packs (see soluble packaging options above)
   • wettable powders (preferably pre-mixed in a slurry)
   • water dispersible granules and dry flowables
2. Maintain agitation and fill the spray tank to three-quarters of the total spray volume. Then add:
   • water-based solutions
   • emulsifiable concentrates or oils
   • spray adjuvants (if indicated on the label)
3. Finish filling the spray tank to the required volume, maintain continuous agitation during mixing and final filling, and throughout application.
4. To prevent oil buildup in the sprayer, empty the tank completely before refilling.
5. Clean the tank and sprayer with a detergent or solvent immediately after use, then flush thoroughly with clean water.

Use caution when mixing different pesticides, or pesticides with fertilizers, unless mixtures are registered for use and recommended on the product label. Tank mixtures of two pesticides registered on the same crop are allowed but done at the user's risk.

Unless specifically mentioned on a product label, use caution when adding adjuvants to a spray solution. Many products have adjuvants in the formulation already, and certain combinations could reduce product effectiveness, increase the likelihood of phytotoxicity or cause the spray to congeal or separate.

Related Links

• Pesticide Application and Safety
• How Weather Conditions Affect Spray Applications Order No. 09-037w
• Six Elements of Effective Spraying in Orchards and Vineyards Order No. 09-039
• Adjusting, Maintaining and Cleaning Airblast Sprayers Order No. 10-069
• The Hidden Cost of Damaged Nozzles
• OMAFRA Sprayer Calibration Calculator
• Grower Pesticide Safety Course Manual
• Pesticide Companies and Agents
• Search the PMRA website
• Ontario Minor Use Program
• OMAFRA Publication 75: Guide To Weed Control: Tree Fruit