While all adjuvants serve to improve crop protection performance, they do so in one of two specific ways. One group, called activator adjuvants, gets its name from what it does: activate crop protection products. The other group, called special purpose/utility adjuvants, serve to make tank mix ingredients work better together. To learn more about special purpose/utility adjuvants, read our blog “Get to Know Adjuvants: Special Purpose/Utility.”

What are Activator Adjuvants?

Activator adjuvants enhance the biological activity of a specific crop protection product. For example, herbicides already have the ability to enter into and kill a weed, depending on their active ingredient formulations. When an activator adjuvant is added to the equation, it helps the herbicide to more readily enter the weed. Crop protection products applied with an activator adjuvant will have increased absorption and penetration rates, allowing for better weed, insect, or disease control. This group of adjuvants includes surfactants, oil concentrates, and liquid fertilizer solutions.

Types of Activator Adjuvants

Surfactants (Wetter-Spreaders)

For best results, pesticides must be able to spread and adequately cover the surface of the pest – for example, the leaf of a weed. Some weeds have very waxy or hairy surfaces, making it difficult for an herbicide to spread out and fully cover a leaf. Surfactants, also known as wetter-spreaders or wetting agents, help to spread herbicide by reducing the surface tension between the spray solution and the target surface. This allows water droplets to spread across the weed’s leaf – for example, increasing the contact area for better absorption. Surfactants are one of the most commonly recommended adjuvants on herbicide labels, especially for water-soluble and systemic herbicides.

Surfactants are categorized by ionic charge. Non-ionic surfactants (NIS) have no ionic charge and are the most common type required on labels. Organo-silicone surfactants are a newer type of surfactant and are often called “super-spreaders” due to their ability to provide greater spreading of spray solutions. Other types include cationic surfactants (positively charged) and anionic surfactants (negatively charged), but they are rarely mentioned on labels.

Oil Concentrates

Pesticides are only effective if their active ingredients can penetrate the target pest, such as an insect’s tough exoskeleton. Traditional crop oils are used more often for insect and disease control than herbicides but can also be used to increase penetration through a waxy leaf coating. Many oil concentrates contain a surfactant, providing the penetration properties of oil and the spreading properties of a surfactant. Choosing the right oil concentrate depends on the source of the oil base required on the product label. Oil concentrates are categorized by the oil source as shown in the chart below.

Liquid Fertilizer Solutions (AMS)

Nitrogen fertilizers like urea ammonium nitrate (UAN) at 28 and 32 percent and ammonium sulfate (AMS) can be added to a tank mix to serve multiple purposes. As an activator adjuvant, it helps to increase the absorption within the target pest, making it more effective. This unique adjuvant can also serve as a special purpose adjuvant, added to condition hard water, enhancing the physical characteristics of the spray solution. The image below shows water containing no surfactant (left) and water containing surfactant (right).

Image courtesy of USDA.

Now more than ever, it’s important for retailers to stay engaged with their CHS Agronomy representative to stay up to date on the latest adjuvant technology in order to select the best adjuvants for their operation and profitability. It’s also important for growers to talk with their agronomist about how adjuvants are vetted, selected, and used to enhance crop protection products applied to their operation.

For more information about adjuvants, download the CHS Agronomy white paper "Using Adjuvants to Improve Crop Protection Performance". For a listing of available adjuvants visit the CHS Agronomy website.