Adjuvants in Pesticides

Adjuvants are added to products to help the pesticide do its job and stay on target. They may be in a formulated product when it's purchased. Or, they may be added to a mixture before it is applied (tank-mixed).

Many adjuvants are surfactants. Surfactants are also called "surface acting agents" or wetter-spreaders. They flatten and spread droplets so that a product can penetrate a leaf.

An adjuvant may be in a product for many reasons, including to:

• Reduce off-site movement (drift) of a product
• Help an herbicide stick to a plant leaf
• Allow a product to penetrate a waxy leaf
• Reduce foaming during mixing
• Control acidity in a tank mixture

Factors to consider:

• Most adjuvants are not required to be listed on pesticide product labels. If included in the mixture, they are considered “other/inert ingredients.”
• Mixtures of ingredients can behave differently in the environment or the body compared to an ingredient alone. For example, some surfactants can increase skin absorption of a product. Or, a mixture may break down faster in soils compared to an ingredient on its own.
• Adjuvant products (tank-mixed) are not registered with the federal EPA. However, some states require registration. Consider contacting your state pesticide regulatory agency for information.
• Always read product label directions. It may state which adjuvants should or can be used with the product.
• A local expert may be able to provide guidance for adjuvant selection.
• A manufacturer may be able to answer questions about tank-mixed adjuvant products.

Additional Resources:

• Spray Adjuvants - PennState Extension
• Adjuvants and the Power of the Spray Droplet - Purdue Extension
• Compendium of Herbicide Adjuvants - Purdue Extension
• Compatibility with Adjuvants - Texas A&M AgriLife Extension
• Adjuvants - University of Florida Extension

If you have questions about this, or any pesticide-related topic, please call NPIC at 800-858-7378 (8:00am - 12:00pm PST), or email us at npic@ace.orst.edu.