Adjuvants 101: Understanding the “Extras” in Your Tank

FBN Network

Oct 09, 2023

When it’s time to apply an herbicide, or maybe a pesticide, insecticide or fungicide, you want to ensure you’re getting the most out of every droplet that leaves the sprayer.

Are you including an adjuvant in your tank mix? How do you know if you should?

What Is an Adjuvant?

An adjuvant is a non-pesticide product added to a spray tank mix that enhances the performance of the spray solution. They often improve spray mix characteristics – such as spreading, penetration or droplet size – or reduce any potential application problems from the spray mix itself, thus increasing effectiveness. Examples of adjuvants include surfactants, oils, buffers, and defoaming agents.

Spray adjuvants can be categorized into two groups: 

  1. Activator adjuvants 

  2. Special purpose adjuvants

Activator Adjuvants

Activator adjuvants improve the action of a pesticide product by encouraging absorption and efficacy. This category of adjuvants includes: 

  • Surfactants

  • Oils 

  • Nitrogen-based fertilizers


Surfactants change the surface tension of a spray droplet. They make the area of pesticide coverage larger, increasing exposure to the chemical. These are useful when applying a pesticide to a plant with waxy or hairy leaves.

Some commonly used surfactants include:

  • Nonionic Surfactants: Compatible with most pesticides - Help pesticide sprays penetrate plant cuticles - Are recommended for most pesticides that require a surfactant

  • Organo-silicone Surfactants: Reduce surface tension, increase spreadability and improve rainfastness


Crop oils promote the penetration of a pesticide spray either through a plant's waxy cuticle. Two commonly used variations are:

  1. Crop oil concentrates (COCs) have the penetration of an oil with the spread of a surfactant. COCs are often used with post-emergence herbicides.

  2. Vegetable oil concentrates (VOCs), in many cases, have gone through a process called esterification, which results in a methylated seed oil (MSO). MSOs work similarly to COCs to increase penetration of the pesticide.

Nitrogen-Based Fertilizers

Adding ammonium sulfate (AMS) or urea-ammonium nitrate (UAN) to a spray mix has been shown to increase the efficacy of some herbicides. Many times, these are available in easier-to-mix liquid forms, which provide more consistent results.

Special Purpose Adjuvants

Special purpose adjuvants correct conditions that can negatively affect the spray solution or application to help optimize pesticide performance. This group of adjuvants includes:

  • Buffers

  • Conditioning Agents

  • Defoaming Agents

  • Stickers

  • Drift Control Agents

  • Foam Makers

  • Tank Cleaners


Most pesticides perform best in slightly acidic spray water with a pH of 4.0 to 6.5. Those in solutions above pH 7.0 are at greater risk of breaking down. Buffers lower the pH of spray water and help stabilize it at a constant level.

Conditioning Agents

Hard water minerals can bind with active ingredients in some pesticides, decreasing pesticide performance. Water conditioners neutralize these minerals and protect the spray mix from this problem. Many conditioners will also include a buffer.

Defoaming Agents

Some pesticides can create foam in spray tanks, often because of the use of a surfactant or the spray tank agitation system. This can be reduced by adding a defoaming agent.


Stickers increase the ability of particles to stick to a surface, decreasing the amount of pesticide that washes off during irrigation or rain. They can also reduce pesticide evaporation and slow degradation of pesticides by UV rays.

Drift Control Agents

Drift control agents improve the placement of pesticide sprays by increasing droplet size, a priority near sensitive sites or when conditions require increased caution.

Foam Makers

When used with special equipment, these adjuvants produce foam to mark where a product was applied, helping avoid missed or overlapping areas.

Tank Cleaners

Tank cleaners work with water and oil-soluble pesticides and are often recommended by pesticide labels.

How Do You Know Which Adjuvant to Include in Your Mix?

Most pesticide labels will include a section to help you decide what type of adjuvants will help you get the most out of your application. These often utilize language such as “required,” recommended,” or “can be used” to help you understand which adjuvants are essential to your mix and which ones are optional.

Before using any adjuvant, always read and follow the accompanying pesticide or other product label. Not all adjuvants are labeled for use in all states, and many adjuvants have crop specific recommendations as well. Violating these instructions is an illegal use of the pesticide and can result in crop damage or poor performance.

Optimize Your Application with Adjuvants from FBN Direct®

Double down on savings and convenience when you shop for adjuvants and other key ag inputs on FBN Direct. Using FBN®’s convenient online store, simply search for the adjuvants you need and immediately see product availability, pricing, labels and other details. Plus, you’ll get direct-to-farm delivery in three days or less. 

Recommended Adjuvants from FBN Direct

  • Farmers First™ Even™ L Pro is an optimized premix of drift management agents, deposition aids, AMS and surfactant. Designed to enhance the performance and activity of pesticide sprays by reducing tie-up of herbicides in hard water, it improves spray application coverage and minimizes spray drift.

  • Farmers First™ FieldGrip™ DRA is a high-concentrate emulsifiable deposition aid and drift management adjuvant.

  • Farmers First™ IN-Plant™ is a crop oil concentrate adjuvant containing paraffinic oil, emulsifiers and surfactants. 


1. Hock, Winand (2015) Spray Adjuvants; Retrieved from

2. Witt, James M. (2012) Agricultural Spray Adjuvants 

Related Resources

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FBN Network

Oct 09, 2023