What is the definition of a filler in the context of pesticides?

In the context of pesticides, a filler refers to a diluent that is used to adjust the concentration of the active ingredient or to enhance the physical characteristics of the pesticide formulation. Fillers can take various forms, including powdered substances that help in distributing the active ingredient evenly during application. This makes them essential for ensuring that the pesticide performs effectively while maintaining safety for the applicator and the environment.

The other options do not accurately represent the role of a filler. An active ingredient is the component responsible for the pesticide's effectiveness against targeted pests rather than a diluent. Pesticide application equipment is related to how these chemicals are dispersed but does not represent the chemical composition of a pesticide. A formulation containing only water does not function as a filler; it may be a carrier or solvent but not a filler by the established definition in pesticide formulations.