Pests include insects, plant pathogens, weeds, mollusks, birds, mammals, fish, nematodes (roundworms) and microbes that compete with humans for food, destroy property, spread or are a vector for disease or cause a nuisance.
Insects, plant pathogens, weeds, mollusks, birds, mammals, fish, nematodes (roundworms), and microbes competing with humans for food, damaging property, spreading diseases, or causing nuisances are all considered pests.