Tank mixing has become a routine part of golf turf maintenance, but have you ever wondered why some combinations work and other don’t?  By understanding a few basic principles, the chemical operator can apply a large number of chemical combinations simultaneously and with confidence.

There is a great economic and performance benefit in being able to spray a mixture of chemicals at the same time.  The beneficial results have at times been astounding, and once the art has been mastered the chemical operator will never go back to the old-fashioned notion that chemicals must be sprayed one at a time because of concerns about phytotoxicity. This need not be the case if one has a thorough, but simple, understanding of the nature of the chemicals one is spraying.

Chemicals can be divided into two categories: solubles and insolubles (assuming water as the substrate).  Generally speaking, insolubles cannot burn grass.  If they are insoluble in water, how can they diffuse into the plant in toxic concentrations? Or how could they be so concentrated as to produce reverse osmosis and have water move out of the plant causing desiccation?  While there are insoluble pre-emergent herbicides that could be sprayed on fine turfgrass and could, over a period of time, release a soluble chemical that could be toxic to a particular species of grass, these precautions are clearly outlined on the label.

Taking this exception into consideration, and following the rule of not exceeding the recommended application rate, one can mix any number of insoluble chemicals in the spray tank without incurring phytotoxicity.

Fortunately, the majority of pesticides are insoluble.  This allows the pest control operator considerable latitude on what can be mixed in the spray tank.  On the other hand, soluble chemicals (pesticides, fertilizers, etc.) must be handled intelligently to avoid phytotoxicity.  One must carefully follow the rules and guidelines in order to avoid burning.

Soluble chemicals can be divided into two general classes: ionic and non-ionic.  The ionic solubles are usually referred to as salts and can be further subdivided into cations and anions.  The cation (positively charged ion) is always accompanied by an anion (negatively charged ion).  They are always found together, neutralizing each other.  For example, 2,4-D can be formulated in various salts.  The 2,4-D acid is considered anionic and the cation is the inert portion whose function is to solubilize 2,4-D in water. 

Compatibility test

Incompatibility results when an active cation is tank mixed with an active anion.  The mixture may become cloudy, form a precipitate or give off heat.  All are indications of incompatibility.  As in the example of 2,4-D, remember that the active ingredient is not the only molecule that may be carrying an electrical charge.  Other chemicals in the ‘inert’ fraction of the formulation may be ions and/or soluble.  For this reason, if you are spraying an active ingredient that you have tank mixed successfully before, you cannot assume that a new formulation of this active ingredient or that every formulation from a different manufacturer is also compatible. Do a jar test and be sure.

When trying new soluble pesticides for possible tank mixing, test them in a glass jar.  If they can be mixed with water and still result in a clear solution, they can generally be safely tank mixed.

When trying new insoluble pesticides for possible tank mixing, they should also be tested in a glass jar. Be sure to add them in the proper order:

 

• Water (see label)

• Wettable Powder

• Dry Flowable

• Liquid/Flowable

• Emulsifiable Concentrate

• Soluble materials

   (fertilizers, pesticides, etc.)

 

Following these basics permits the end user to tank mix a tremendous variety of chemicals, saving time and improving turf health and protection.

Orl start the application as a preventative spray at two week intervals and repeat as required.

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