What is defined as a substance used to destroy, repel, or prevent pests?

The correct answer is the term that encompasses any substance specifically formulated to manage pests, which can include insects, weeds, fungi, and other unwanted organisms. This term reflects a broad category of products that include insecticides, herbicides, fungicides, and more, all aimed at controlling pest populations.

Fertilizers, on the other hand, are substances used to supply essential nutrients to plants, promoting growth rather than managing pest populations. Herbicides specifically target and kill unwanted plants or weeds, while insect repellents are designed to deter insects rather than destroy them. Therefore, the term that accurately captures the purpose of destroying, repelling, or preventing pests in a comprehensive manner is indeed pesticide.