Adjuvants are chemicals that do not possess pesticidal activity. Adjuvants are are either premixed in the pesticide formulation or added to the spray tank to improve mixing or application or to enhance pesticidal performance. They are used extensively in products designed for foliar applications. Adjuvants can be used to customize the formulation to specific needs and compensate for local conditions.

The right adjuvant may reduce or even eliminate spray-application problems, thereby improving overall pesticide efficacy. Because adjuvants themselves have no pesticidal properties, they are not registered by the EPA. As a result, there is no set of standards for composition and quality, although some states have modified registration requirements for these chemicals and may require labels, technical data sheets, and efficacy information.

Before using any adjuvant, consult the pesticide label. Many registered pesticide products have very specific recommendations on their labels for use with one or more adjuvants. Failure to follow these instructions is as much a violation of the product label as inappropriate use of the pesticide.

If you have questions about the specific properties of an adjuvant, contact the manufacturer before attempting to use it. Companies that produce adjuvants can provide labels, technical data sheets, Material Safety Data Sheets (MSDSs), supplemental labeling, and promotional literature about their products.

Adjuvants are designed to perform specific functions, including wetting, spreading, sticking, reducing evaporation, reducing volatilization, buffering, emulsifying, dispersing, reducing spray drift, and reducing foaming. No single adjuvant can perform all these functions, but compatible adjuvants often can be combined to perform multiple functions simultaneously.

Much of the confusion surrounding adjuvants can be attributed to the lack of understanding of associated terminology. For example, many people use the terms "adjuvant" and "surfactant" interchangeably. These terms can refer to the same product because all surfactants are adjuvants; however, not all adjuvants are surfactants.

Adapted from Illinois Pesticide Review, November-December 2008, Dr. Phil Nixon