Which group of pests does NOT include insects?

The correct answer identifies a group that does not include insects. Insects are a distinct category of pests, comprising organisms within the class Insecta, characterized by their six legs, three body segments, and typically possessing wings.

The other groups listed—snails and slugs, vertebrates, and plant disease agents—consist of organisms that lie outside the definition of insects. Snails and slugs belong to the mollusk group and are classified as gastropods, which are entirely different from insects. Vertebrates encompass a broad range of animals with a backbone, including mammals, birds, reptiles, amphibians, and fish, again distinctly different from insects. Finally, plant disease agents, including fungi, bacteria, and viruses, are microorganisms rather than insects. Thus, the selection of the group that does not include insects is accurate, as it separates insects from the other classifications of pests.