What term is used for the active ingredient or its breakdown products that stay on or in the target after pesticide application?

The term "residue" specifically refers to the active ingredient of a pesticide or its breakdown products that remain on or within the target organism after the pesticide has been applied. This includes any remnants of the pesticide that might persist on vegetables, fruits, or surfaces, as well as within the environment. The presence of pesticide residue is a critical aspect of pest management because it can affect not only the ongoing effectiveness of the treatment but also the safety for humans, animals, and the ecosystem.

In contrast, other terms presented do not accurately define this concept. A contaminant generally refers to any unwanted substance present in a sample, and while it can include pesticide residues, it lacks the specificity required in this context. A residual effect describes the continuing effectiveness of a pesticide after its application but does not denote the actual substances remaining. "Leftover chemical" is too vague and informal, lacking the specificity and technical precision associated with the study of pesticides and their residues. Therefore, "residue" is the most accurate term that encompasses the essence of what remains after pesticide application.