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Mixing pesticides in the wrong order can result in the formation of precipitates or other nasty goo.

Eric Prostko

June 16, 2021

2 Min Read
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Brad Haire

Someone once asked me what I thought it takes to be a successful American farmer.  It’s very complicated.  Most farmers I know personally have abundant faith in God, but they also must be a part-time agronomist, chemist, entomologist, plant pathologist, engineer, economist, soil scientist, weed scientist and climatologist. Lots of balls to juggle and plenty of opportunity to drop a few. Our country is lucky to have folks who have the guts to do this 365/24/7! 

For this month, I would like to remind you once again of the importance of mixing sequence when it comes to applying several pesticides at one time in a single application. Mixing pesticides in the wrong order can result in the formation of precipitates or other nasty goo that can jam up an 800-gallon sprayer pretty quickly. Not a good day when that happens!

I was reminded of this issue personally when I tried to spray my own small pecan orchard with a mixture of Roundup and Alion (Figure 1). 

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Left = Alion SC then RoundupPowerMax3 (correct mixing order). Right = RoundupPowerMax3 then Alion SC (incorrect mixing order). Credit: Eric Prostko.

Also, I have been privy to a few other unfortunate mixing catastrophes over the past month (Figure 2).  FYI, not picking on any one product here since this can happen with any and pesticide mixed incorrectly. 

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Left = Roundup PowerMax3 then Zidua SC (incorrect mixing order). Right = Zidua SC then Roundup PowerMax3 (correct mixing order). Credit: Eric Prostko.

The best place for you to get mixing sequence/order information is the pesticide label. If you look hard enough, you might also discover a few helpful cell phone apps.  Your friendly neighborhood county extension agent can also assist you as well. 

It can vary slightly depending upon products, but the general formulation science mixing order is:

  1. Water soluble bags (WSB)

  2. Water soluble granules (WSG)

  3. Water dispersible granules (WG, XP, DF)

  4. Wettable powders (WP)

  5. Water based suspension concentrates/aqueous flowables (SC, F)

  6. Water soluble concentrates (SL)

  7. Suspoemulsions (SE)

  8. Oil-based suspension concentrates (OD)

  9. Emulsifiable concentrates (EC)

  10. Surfactants, oils, adjuvants

  11. Soluble fertilizers

  12. Drift retardants

In the heat of the pest management battle, it is often easy to overlook the importance of mixing sequence when tank-mixing various pesticides.  When the wind is blowing hard or it is too dry/hot, mixing order is probably the last thing on someone’s mind.  By taking some time to review the label beforehand, phoning a friend, or using a cell phone app, tank-mixing mishaps can be avoided. 

(My apologies to my regular readers for missing my May 2021 Tailgate Talk.  Like most of you, I have been busy planting, spraying, and worrying about the weather (too cold, too hot, too dry, too wet, and too windy).  Also, I have been writing popular press articles for so long it has been difficult for me to come up with new topics that I have not already discussed. I would welcome any suggestions - [email protected].)

As always, good weed hunting!

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