Sequential treatments are much like ‘cuss’ words to most peanut growers and tank-mixing is too often music to their ears, says North Carolina State University Peanut Specialist David Jordan.

It’s difficult to tank-mix more than two materials and make an application at the best time to provide optimum control of the target pests. Usually tank-mixing requires the grower to determine whether he or she can live with less than complete control of one or more pests, Jordan says.

Sometimes the reduction in control is due to a lack of compatibility of materials in the tank-mix.

But often times it’s a case of you thinking everything is ready to be sprayed at that one time you decide to apply a tank-mix.

In reality, most of the time you are a little early for one thing and a little late for something else.

“As long as the grower understands the tradeoff and can live with the results, tank-mixing can be a good thing,” Jordan says.

Once you get into tank-mixing multiple, especially 3, 4 or 5 products, efficacy becomes a guessing game, and it’s hard to determine which material is doing the job and which one isn’t and knowing exactly what will happen.

Peanut growers have 19 different active ingredients for herbicides alone, plus multiple and different means of application and recommended timing of application.

Insecticides bring another 16 options and there are at least 20 fungicide options. Without adding in Apogee and other specialty products and fertilizers, or multiple application strategies used on peanuts, that brings the total tank-mix options to over 6,000.

In most cases most tank mixes are biologically and physically compatible. Biologically, you are going to control the target pest at some level without damaging the plant.

Physically, these materials will mix smoothly without precipitates forming, stopping up spray equipment or some other physical problem.

However, Jordan says there are some wild cards — water quality such as softness or harness and pH. 

Spray volume, adjuvant selection and formulation can also play a role in compatibility. For example, is the formulation of the product more important than the active ingredient?

For example, with chlorthalonil formulations the formulation may have a bigger effect on how well the tank-mixed herbicide works more so than the active ingredient, Jordan says.

Adjuvants can have a big impact on how well one pesticide works versus another material in a tank-mix.

For example, the grower may want a fungicide to move through the canopy to reach the soil-borne pathogen. But mixing a fungicide with a herbicide and the appropriate adjuvant for the herbicide can keep the fungicide on leaves and minimize efficacy of the material.

With herbicides in a tank-mix, timing of application is always an issue. If a grower applies the tank-mix when weeds are small, the loss in efficacy from the tank-mix may not be a big deal.