Saving labor and enhancing the effectiveness of pesticides are two primary reasons for tank mixing them. Seems like an easy thing to do, but you must keep in mind that you are dealing with chemicals, and as you may recall from high school chemistry, sometimes mixing the wrong things together leads to unhappy results. Mixtures that turn to solids, mixtures that refuse to stay mixed and mixtures that are toxic to the handler or to the plants are just a few of the ways improper mixing can go wrong. Before attempting to mix anything — do your research! Read the label and follow these basic principles:

  1. Read the label! I know it was mentioned already, but the label is your source for all kinds of vital and legal information. The label will tell you if you can mix the pesticide with other pesticides or fertilizers.

  2. Jar test. If the label does not provide mixing instructions and if you are not sure of the response of the chemicals or the plants toward the mix, perform a jar test. Mix the pesticides and additives in the appropriate order and proportion (see below), shake and allow to sit for an hour. If the jar heats up, chemical changes are taking place and the combination is probably not suitable for mixing. Look for any type of precipitate, including clumps, flakes, gels or layering. Any of these situations indicate the pesticides are not compatible and should not be used together.

  3. Test Application. Apply the contents of your jar mix to a small population of target plants to test for phytotoxicity or undesirable residue. You may need to wait a few days for symptoms to be apparent.

  4. Fertilizers can be used with some pesticides in some situations. Read the label and perform the jar test to determine if fertilizers can be mixed. Use caution because some fertilizers can dramatically change the pH of the mixture and cause the pesticides to react in an undesirable way.

  5. Keep in mind that the labeled pesticide rate must be followed whether you use the product alone or in a mix. It is illegal to mix a higher concentration of pesticide than the labeled rate.

  6. Mixing order is extremely important. Some pesticides can be combined only if they are mixed in the proper order. If not, incompatibility and potential toxicity to the handler may develop. The label may provide mixing directions. If not, use the following guideline:

    • Fill spray tank to ½ total volume and begin agitation.

    • Add wettable powders (WP), then dry flowables (DF), then flowables (F) then liquids (L), in this order. You may want to line up the products according to this order to help you stay organized. Allow solution to mix thoroughly after each addition.

    • Fill tank to ¾ total volume.

    • Add any emulsifiable concentrates (EC). Mix thoroughly.

    • Add any crop oils, adjuvants, surfactant or liquid fertilizers. Mix thoroughly.

    • Fill tank to final volume.

  7. Keep records of reactions, compatibility and effectiveness. If you find a good combination, you'll want to repeat it.

Want to use this article? Click here for options!
© 2020 Penton Media Inc.

Interactive Products

Equipment Blue Book

Used Equipment Valuation Guide

Riding mowers, lawn tractors, snow throwers, golf carts


Grounds Maintenance Jobs

search our jobs database, upload your resume