What term describes how pesticides kill pests by targeting specific biological systems?

The term that describes how pesticides kill pests by targeting specific biological systems is "mode of action." This concept refers to the specific biochemical mechanism through which a pesticide exerts its effects on a pest. Understanding the mode of action is crucial for several reasons, including developing effective pest management strategies, minimizing resistance development in pest populations, and selecting the right pesticide for a particular application.

"Site of action" refers to the specific location within the pest’s body where the pesticide interacts; it's a narrower concept than mode of action. "Behavioral response" relates to how pests might change their behavior in reaction to pesticides or environmental changes, which is not specifically about the biochemical mechanisms of toxicity. "Active ingredient" pertains to the chemical component of a pesticide that has the ability to kill or control pests, but it does not encapsulate the process or pathway by which that action occurs. Thus, mode of action is the most comprehensive term that encompasses the way pesticides function at a biological level to eliminate pests.