Which of the following is NOT a type of extender adjuvant?

The correct choice, which identifies an option that is not a type of extender adjuvant, refers to stickiness modifiers. Extender adjuvants are substances that are added to pesticides to improve their performance and longevity. They primarily work by extending the effectiveness of the active ingredients through better adherence to surfaces and prolonging their action.

Surfactants, buffers, and plant penetrants are all types of extender adjuvants. Surfactants reduce surface tension, allowing the pesticide to spread more evenly over surfaces. Buffers help maintain the pH of the spray solution, which can affect the stability and efficacy of certain pesticides. Plant penetrants enhance the ability of the pesticide to penetrate plant tissues, leading to improved absorption of the active ingredients.

Stickiness modifiers, while they might be used in agricultural practices, do not fit the definition of extender adjuvants specifically. They might influence how products adhere to surfaces, but they don't have the same role in extending the functionality or longevity of the pesticide applications as the other listed adjuvants do. Understanding these distinctions is important for applying pesticides effectively while maintaining safety and compliance with regulations.