A __________ is any chemical used to control pests.

The term that best fits the description of any chemical used to control pests is pesticide. Pesticides encompass a broad category of substances designed to deter, incapacitate, or kill pests, which can include insects, weeds, fungi, and other organisms deemed undesirable in agricultural and residential settings. This definition highlights the versatility of pesticides, as they can take various forms and serve multiple purposes in pest control.

While an insecticide specifically targets insects, a herbicide focuses on controlling unwanted plants, and a fertilizer is used to supply nutrients to plants, these terms are more specialized and do not capture the full range of substances classified as pesticides. Therefore, pesticide is the most comprehensive term for any chemical intended to manage pest populations effectively.