Adjuvants cause pesticides to stick to plants, spread over leaves or penetrate plant material. Types of adjuvants include wetting agents, surfactants, stickers, extenders and plant penetrants. The terminology can get confusing because several of these actually do the same thing. For instance, wetting agents and surfactants (the most common of the adjuvants) are interchangeable. Surfactants can be cationic, anionic or nonionic, depending on their charge, and there are different instances of use for each. Never use a positively-charged cationic surfactant as a stand-alone because it can can be phytotoxic. Negatively-charged anionic surfactants work well with contact pesticides. Nonionic surfactants have no charge and are compatible with most pesticides. Failure to select the correct surfactant can result in damage to plants or, at the very least, can reduce the efficacy of pesticides, so be sure to read the label before mixing one in. (Many pesticide products will specifically recommend the use of one or more adjuvants, so consulting the label is critical.)
The follow table outlines the various types of adjuvants available, and describes their uses. As you review the products listed under each category, you may notice several of them listed in more than one category. This is because manufacturers often will blend active ingredients to make their adjuvants fill more than one need (yet another reason to check the label on your pesticide).
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