A __________ is any chemical used to control pests.

The term that fits the description of "any chemical used to control pests" is pesticide. Pesticides encompass a broad category that includes substances aimed at managing various types of pests, which can range from insects and weeds to fungi.

In more detailed terms, pesticides are classified into different kinds based on what they are primarily targeting. For instance, insecticides specifically target insects, herbicides focus on weeds, and fungicides deal with fungal infections. While all the other options are examples of pesticides, none of them is as general or inclusive as the term pesticide itself, which covers all pest control chemicals. Therefore, the correct choice signifies the overarching category, making it the best answer to the question.