Adjuvants

Adjuvants are chemicals added to pesticide spray mixtures to enhance or modify the pesticide and/or physical properties of the pesticide or the spray mix. When used alone, adjuvants have no pesticidal properties.

More than 200 EPA registered pesticides have very specific recommendations on their labels for the use of one or more adjuvants. These recommendations are for different types of adjuvants and are recommended for one of two reasons—or both—to affect pesticide efficacy, or to reduce, minimize or eliminate spray application problems. The benefits of these two functions are to help negate pesticide non-performance and/or crop injury.

Your consistent, effective results from the use of adjuvants will depend upon selecting, first, the right type of adjuvant and secondly, the best suited product within that type for your use.

Terminology

Much of the confusion concerning adjuvants comes from the lack of understanding of adjuvant terminology. Many people use the terms adjuvant and surfactant interchangeably and although they can refer to the same product, it should be remembered that all surfactants are adjuvants, but not all adjuvants are surfactants! Understanding adjuvant terminology can help you obtain the optimum pesticide performance. When a pesticide label requires a "crop oil concentrate" and you use a "crop oil" instead, you may not be satisfied with the results.

Another example of the importance of understanding the terminology is the fact that pesticide activity in the presence of a "nonionic surfactant" can be tremendously different than when in the presence of just a "surfactant" that could be anionic or cationic in nature. Most EPA registered pesticides that require "surfactant" usage recommend a "nonionic" type.

Spray Application

Spray application is perhaps the weakest link in the chain of events a pesticide follows through its synthesis, testing, registration and final use. It is the final controllable event in most pesticide spray programs. Some researcher claim that up to 70% of the effectiveness of a pesticide can be dependent on spray application. The reason spray application has such an effect on pesticide effectiveness is better understood when one examines pesticide characteristics, such as stability, incompatibility, solubility, suspension, foaming, drift, evaporation, volatilization, degradation, adherence, penetration, surface tension, coverage, and others. Many of these problems are visible to the applicator (i.e., foaming, incompatibility) and corrective measures are applied whenever they present themselves. However, other problems are not visible to the applicator (i.e., evaporation, degradation) but may have an even greater influence on pesticide efficacy than those that are. Researchers as well as applicators have well documented that these problems do exist and that corrective measures can be made that will offset their negative effect.

Adjuvants can reduce, minimize or eliminate many spray application problems. They can do this because adjuvants are designed to perform specific functions. These functions include wetting, spreading, sticking, reducing evaporation, reducing volatilization, buffering, emulsifying, dispersing, reducing spray drift, reducing foaming, and others.

Pesticide Labels and Adjuvant Recommendations

The need for adjuvants is, for the most part, determined by requirements, recommendations or suggestions of pesticide label information. The pesticide label should be consulted before any adjuvant use has been determined.

If you review pesticide labeling, adjuvant information will usually fall into the following categories.

• Pesticide labels that require the use of adjuvants.
• Pesticide labels that suggest the use of adjuvants.
• Pesticide labels that prohibit the use of adjuvants.
• Pesticide labels that neither require nor suggest adjuvant usage, but, on the other hand, do not prohibit adjuvant usage. These labels are void of adjuvant information.
• Pesticide labels that contain a combination of some or all of the previously listed information.
• Pesticide labels that when used alone, are void of adjuvant recommendations or prohibitions, but when tank-mixed with other pesticides acquire some or all of the previously listed information. Where two or more pesticides containing adjuvant recommendations are tank-mixed, the one with the most restrictive labeling takes precedence.

Technical literature, technical data sheets, material safety data sheets (MSDS) supplemental labels and promotional literature are other sources of adjuvant information.