Humans share the planet earth with some 10 million species of organisms. Each species eats, grows and reproduces in different ways in different locations around the world but virtually no species does this in isolation. All species are interconnected to some extent, with some organisms more dependent on others, especially those higher in the food chain. Tigers would not live long without their prey being available, just as rabbits would not survive for long without plants to eat. Humans have quite a dominant position in many ecosystems and they depend on many other species for food and shelter. Especially because the influence of humans is so pervasive throughout the world, humans also compete with many organisms and we generally think of many of these competitors as “pests.”

Man has been plagued by “pests” since time began. A pest can be formally defined as any organism that reduces the availability, quality, or value of some human resource (Flint & van den Bosch, 1981). The definition of pest needs to be broad due to the great diversity in the ways that pests affect humans. The resources in question can be a plant or animal grown for food, fiber or pleasure (e.g., pets, plants in recreation areas). Another resource is human health and well-being, making organisms directly affecting human health, such as mosquitoes, pests too. Pests are as diverse taxonomically, ranging from microorganisms to mammals, as they are in the ways that they compete with humans.