Making Sense (Cents) of Tank-Mixing

Tank-mixing pesticides is one of the many ways farmers try to increase efficiency each year. But just because we can do something doesn’t mean we should be doing it. Does tank-mixing pesticides make sense, or rather, cents, in field crops?

Combining products in the tank and reducing the number of trips across the field is convenient. There are many benefits to this strategy, including reduced mechanical injury to plants, reduced soil compaction, and cost savings for fuel and labor. Additionally, tank-mixing makes sense for some pest scenarios, like using multiple herbicide active ingredients to target different types of weeds and combat resistance. However, there are several environmental and financial reasons not to tank-mix in field crops, and the consequences could outweigh the benefits in some cases, especially for insecticides.

It is challenging to target insect, disease, and weed pests together at their most susceptible timings with a single application. At this point in the season, many fungicides are being applied to fields, and an insecticide is often included to save on application costs. But this practice is likely not the best option for insect pest management or long-term resistance management. 

Use Scouting and Thresholds

The keystone of a sustainable pest management plan is to be aware of pest activity and yield loss potential. This concept is especially true for insects. Ensuring pests are active in the field and abundant enough to warrant an insecticide application is critical for profitable and effective pest management. Understanding the true cost of an application (dollars per acre) will help determine if an application is justified based on future market values (dollars per bushel). A foliar insecticide application aims to protect yield, and hopefully, the effort results in a profitable choice.

Insecticides offer no value to the plant except to suppress pests, so there has to be a certain number of pests present to meet an economic threshold. Prophylactic, tank-mixed sprays often miss the mark for insect suppression because they are applied too soon. The odds of breaking even on an insecticide applied too soon are small compared to a well-timed treatment. 

Pest Resistance is a Concern

Every pesticide application is an exposure to target and non-target pests and an opportunity for those pests to develop resistance. It is happening and intensifying for weeds, plant pathogens, and insects in field crops worldwide. Minimizing unnecessary applications will prolong the efficacy of available and affordable pesticides. Resistance to insecticides is often irreversible, and alternative group numbers are usually significantly more expensive. Additionally, regulatory action threatens the availability of certain active ingredients or groups of insecticides, further limiting options in the face of resistance development. Consider these long-term impacts of a “cheap” insecticide application before deciding to tank-mix.

Further Considerations

Other deliberations for tank-mixing pesticides are product compatibility and mixing order. Just because we can combine multiple products doesn’t mean the result will be successful. Be aware of synergistic crop damage, antagonism, and physical issues with mixing chemistries. Finding sludge or sediment, or seeing phytotoxicity, is a negative consequence of application mishaps. Plus, the equipment cleanup for incompatible products can be time-intensive. Conducting a jar test before loading a full tank of a new tank mixture is a best practice to ensure physical compatibility, but it cannot quickly determine whether chemical synergism or antagonism will occur.

*This article was originally posted in Progressive Farmer/Wallaces Farmer in June 2025.