Which term describes a chemical used to control pests?

The term that describes a chemical used to control pests is "pesticide." This is a broad category that encompasses a variety of substances designed to manage different types of pests that may cause harm to crops, humans, or the environment. Pesticides can include various specialized formulations targeted at insects, weeds, fungi, and other organisms that are considered pests.

While other terms provided, such as insecticide, herbicide, and fungicide, refer to specific types of pesticides—each tailored for a particular kind of pest—the overall term "pesticide" is the most accurate choice to cover all these categories collectively. Insecticides specifically target insect pests, herbicides focus on unwanted plants (weeds), and fungicides are aimed at controlling fungal infections. Thus, "pesticide" serves as the umbrella term for all these substances, making it the correct answer in this context.