Which term describes a chemical that hinders pest development or kills pests?

The correct term to describe a chemical that hinders pest development or kills pests is the active ingredient. Active ingredients are specifically designed to have a direct effect on pests by disrupting their biological processes, leading to their control or destruction. These are the core components of pesticides that provide their intended effectiveness against target organisms, such as insects, weeds, or diseases.

In contrast, inert ingredients are substances present in a pesticide formulation that do not have a pesticidal effect themselves. They can serve various roles, such as aiding in the dispersion or stability of the active ingredient but do not contribute to the pest control efficacy directly. Secondary ingredient is not a standard term used in pesticide formulations and may lead to confusion regarding its role. Adjuvants, while important in enhancing the effectiveness or application of pesticides, do not directly kill pests or hinder their development in the same way as active ingredients do. Adjuvants can improve the performance of the active ingredient by modifying its properties, such as increasing its adherence to surfaces or improving its penetration, but they do not function as pesticides themselves. This distinction highlights why the active ingredient is the correct choice in describing substances that directly impact pest populations.