Which of the following is not a main group of pests?

Viruses are classified as pathogens rather than being a main group of pests. In the context of pest management, the primary groups are typically categorized as weeds, pathogens, and invertebrates. Weeds obstruct agricultural productivity by competing for resources, pathogens, such as fungi and bacteria, cause diseases in plants and animals, while invertebrates include a variety of pests like insects, mites, and nematodes that can damage crops.

Viruses, while they can infect and harm plants and animals, are not classified as a main group of pests because they do not fit into the broader categories used for pest management purposes. Instead, they are a specific type of pathogen, which is a category that encompasses a variety of disease-causing microorganisms, including fungi, bacteria, and viruses. Thus, identifying viruses as a separate group from the primary categories of weeds, pathogens, and invertebrates is what makes the choice accurate.