Fact Sheets

Herbicide Tank Mixtures – Inert Ingredients and Adjuvants

Pesticide formulations (the commercial product that users purchase, e.g., Chopper®, Accord® XRT II) contain both active and inert ingredients. Active ingredients directly control pests. For example, the forestry herbicide formulations Chopper® and Arsenal® contain the active ingredient imazapyr, which inhibits plants’ ability to synthesize some amino acids essential for growth.

Inert ingredients do not have direct herbicidal effects on plants, but they enhance the effectiveness of active ingredients and improve the product’s performance. The term “inert” does not mean that a substance is non-toxic, it simply means that it does not have any direct pesticidal effect. Another term used for inert ingredients is “adjuvant,” although in practice, “inert ingredient” seems to be used mostly for substances that are premixed in the formulation (i.e., added by the manufacturer during the manufacturing process). The term “adjuvant” is more commonly used to describe substances that are added directly to the spray tank mixture by applicators.

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