Are you adding additional surfactant to your herbicide package?

Glyphosate is a herbicide that comes fully loaded with an adjuvant package. Because we have had so many acres treated with glyphosate alone over the last 15 years, I believe we may have forgotten the importance of adjuvants in the tank for maximizing herbicide performance. I would challenge you to talk with your crop protection retailer and make sure you know EXACTLY which adjuvant is the best one for the herbicides you are using in 2018. And ask what the difference is between NIS, MSO, COC or an HSOC. Not sure? Maybe you want to learn more?

I would recommend going to this website: Also, below is my take on the importance of adjuvants for maximizing herbicide performance.

Importance of adjuvants for maximizing herbicide performance: What is an adjuvant exactly? An adjuvant is any additive used in conjunction with a pesticide to increase biological activity and/or to modify various physical properties of a spray solution. Using the proper adjuvant for a given pesticide is extremely important. Using the wrong adjuvant with a herbicide, for instance, can make a huge difference in weed control and could very well create a situation where a field needs to be re-sprayed, or it could cause yield reduction due to weed competition. Adjuvants may not be the most expensive product in the tank, but they could cause the most expensive product in the tank to not perform to its maximum capabilities.

The picture below shows some of functions that an adjuvant may be asked to do to maximize performance of the pesticide.


Adjuvant Classes:

  • Surfactants (also called spreaders or wetting agents): An adjuvant that reduces surface tension between the spray solution droplets and the pest target’s surface, thus providing greater coverage.
  • Crop Oil Concentrates: A combination of oil (petroleum or vegetable) and surfactants/emulsifiers. Crop oil concentrates act as penetrants, stickers, spreaders (limited), humectants, etc.
  • Methylated or Ethylated Seed Oils: An emulsified methylated or ethylated seed oil. Act as penetrants, spreaders (limited), humectants, etc.

This picture depicts what an adjuvant does on a leaf surface.


I am sure many of you are familiar with the disease triangle. The disease triangle says that you must have 3 things to have a fungal disease: the disease pathogen, a susceptible host and the proper environment. We have something similar for weed control. It is called the weed control diamond. It looks like this:


Weed Control Diamond – To get the weed control you desire, you must have 4 things:

  • Plants: The weeds must be susceptible to the herbicide used, and the crop needs to be able to tolerate the herbicide. In other words, the weeds must be the right species for the herbicide and be the correct size for the rate of herbicide used. Also, the crop needs to be tolerant at the proper application timing for the herbicide.
  • Herbicide: The herbicide needs to be the correct herbicide for the target weeds and needs to be in the tank at the correct rate.
  • Environment: We all know that the environment plays a huge role in the performance of herbicides. To summarize this part of the weed control diamond, the weather needs to be conducive for the herbicide to work in the target weeds species. Temperature, moisture, sunlight and humidity can all play a role.
  • Adjuvant: As previously discussed, proper adjuvants are extremely important to see the true performance of a herbicide. (FYI – This is also true for insecticides and fungicides as well). Every herbicide label has a section that describes the proper adjuvant package for maximum performance of that herbicide. The adjuvant needed for maximum performance of a herbicide depends on how the herbicide works in the plant. I highly encourage you to read and follow those recommendations.

As we move away from a “Roundup®-only world” it is important to understand what adjuvants are needed for herbicide performance. This is especially true for the tough weed species we have today like marestail, waterhemp and Palmer amaranth. I believe we may have lost focus on this important piece of herbicide performance. I encourage you to study the herbicide labels and discuss with your crop protection retailer the adjuvants that are required. Remember, trying to save a little on adjuvants may cost you a lot in the end.

Also, Illinois happens to be a state that does not require registration of adjuvants. This means that adjuvants do not need to have data to back up their performance claims in our state. In other words, not all adjuvants are created equal. This is one reason why I recommend discussing your adjuvants with your crop protection retailer. They are the experts when it comes to adjuvants for proper herbicide performance.

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About the Author: Eric Ifft

Eric Ifft has been a technical consultant with Bayer CropScience since 2008. Contact him at or 309-825-3730.