Keep your cocktails for happy hour: the perils of complex tank mixing!

Shawn P. Conley, Jed Colquhoun, and Damon Smith; UW Madison Professors and State Extension Specialists

#Plant24 is “On Like Donkey Kong” so we thought it would be a good to remind growers to keep your cocktails for happy hour and consider the perils of complex tank mixing!

Adding something “extra” to the spray tank is not a new or novel phenomenon in agriculture; however, in today’s economic, social, and regulatory environment it is in agriculture’s best interest to think twice before blindly adhering to this mentality. Dr. Paul Mitchell, UW Ag Economist and Associate Dean, terms this practice “the more-on principle”. In its simplest form, this principle is founded on the belief that the more I put on the less downside risk my operation will be exposed to. This “more-on principle” is usually sold as or purchased under the guise of “cheap insurance” for farmers. What makes this principle more appealing is that the extra input is often priced in the 0.5 to 1 bu price for soybean or 2-3 bu price of corn. It is usually conveniently priced so a researcher, farmer, or crop consultant can’t effectively measure if the product paid for itself or not. Not surprising to anyone, these one-off products are internally referred to as profit centers.

The “more-on principle” is risky enough as a one-off addition to a tank-mix, but we are now starting to see multiple products added to the tank. Without further investigation, the farmer may not know what they are applying. To make it worse, the products are often applied at rates that are ineffective. To frame this more explicitly, a common practice this summer in field corn was to offer a farmer a tank-mix that included a fully loaded fungicide, an insecticide (in absence of any insect pests), a foliar feed product, (in the absence of any nutrient deficiency and at fertilizer rates that are known to be ineffective), and additional adjuvant (because it is a well know profit center) at a cost of ~$50 per acre. We won’t even broach the soybean programs containing fully loaded fungicides, insecticides, micronutrient packs, biologicals, and sugar components or the specialty crops where 8-way mixes aren’t uncommon!

So what damage is the “more-on principle” bringing to the ag sector? The first negative hit to a farmer is economic. The custom suite of products is often sold to the farmer as a program. The farmer is expected to either buy the entire program as is or they must wait until the end of the spray cycle to get their off-program applications. It is also difficult to verify if the program worked because often there isn’t a yield-check strip. This challenge is further confounded with genetic yield-gain in most crops, that regardless of inputs, will lead to increased yield over last. So, the real question is ‘did this suite of practices really work?’ To be frank, probably not. For example, we tested the hypothesis that high-input soybean systems provide greater yield and economic stability to farmers. What we found was that intensive management input systems minimally reduced the average cost of yield risk (<3% of average yield) and did not consistently protect soybean yield from downside yield risk, which is counter to what the “more-on principle” would say. See more here!

The next downside peril is increased risk of pesticide resistance. In the example above, an insecticide was added to the tank-mix in the absence of a known insect threshold/pest issue. This not only increases selection pressure for insecticide resistance but also damages the beneficial insect population. The use of insecticide in this case makes the problem worse! We also see this with the use of fungicides, where inappropriate product choices have been used because they were “cheap insurance.” While this sounds good, using the wrong product can make a disease worse. Growers should know what is being sprayed and be sure that the product has been verified to be effective for the target you are after.

In the above scenario we also run the risk of decreased pesticide efficacy due to potential compatibility issues. Not only does this lead to decreased pesticide efficacy and increased resistance issues, but it also can result in registrants’ walking away from issues due to incompatibility issues. In some cases, complex, untested multi-product tank mixes can sometimes even cause crop injury or malformed development.  For example, we’ve seen cases in cranberries where a new and unknown adjuvant in an herbicide mix fused the cranberry blossoms to the point where they couldn’t be pollinated and didn’t produce a crop.

Lastly and even scarier is the increased risk of metabolic resistance, where pesticide applications can ramp up general enzymes in pests that “digest” subsequent applications such that they’re ineffective. This is a scary deal check it out here! The cherry on top of this story of peril is that the pesticide pipeline is very slim. The path to new pesticides, especially novel classes of active ingredients, is nearly non-existent. Also coming along are possible new regulations regarding the Endangered Species Act and agricultural pesticide use. While still open for public comment and potential revisions, there are regulations being considered that will heavily restrict the use of pesticides especially near water and where endangered species are known to exist. Careless use of pesticide applications as described above merely adds to the reasoning to further restrict pesticide use in agriculture.

Finally, it’s important to consider the greater social implications. In agriculture we often pat ourselves on the back and tell everyone we are sustainable and are feeding the world. We can do, and be, better when it comes to using research-based decision making to use inputs only when and where they’re warranted and effective.

If you are a farmer and you wish to explore alternative inputs and complex tank mixes, we are not entirely against this practice, but suggest considering the following before you pull the input trigger.

  1. Know what you are buying (know the active ingredient and don’t let sellers get away with the excuse that it is proprietary). For pesticides, remember that the label is the law with use directions that need to be followed and often dictate tank mix options.
  2. Know the mechanism of action (i.e. what is the input going to do, and is that a verified issue for your crop situation?).
  3. Have independent data showing yield results and efficacy, not just the pretty sales brochure from the company showing huge yield differences with no statistics.
  4. Work with your regional educator, crop consultant or CCA and leave a check strip to see for yourself under your management techniques. Observe the treated area compared to the check strip for pest control, crop development and any potential crop injury.  Tank mixes can sometimes be synergistic and result in crop injury or antagonistic in ways that reduce target pest control.  Most complex tank mixes with several products haven’t been tested extensively.

Though this quote wasn’t meant for this application we think it is definitely apropos: “Protectionism is the Institutionalization of Economic Failure” – Edward Heath