The Gardening Guide

Biological control of pests in agriculture is a method of controlling pests (including insects, mites, weeds and plant diseases) that relies on predation, parasitism, herbivory, or other  natural mechanisms. It can be an important component of integrated pest management (IPM) programs.

Biological Control is defined as the reduction of pest populations by  natural  enemies and typically involves an active human role.  Natural  enemies of insect pests, also known as  biological control agents, include predators, parasitoids, and pathogens.  Biological control agents of plant diseases are most often referred to as antagonists.  Biological control agents of weeds include herbivores and plant pathogens. Predators, such as lady beetles and lacewings, are mainly free-living species that consume a large number of prey during their lifetime. Parasitoids are species whose immature stage develops on or within a single insect host, ultimately killing the host. Most have a very narrow host range. Many species of wasps and some flies are parasitoids. Pathogens are disease-causing organisms including bacteria, fungi, and viruses. They kill or debilitate their host and are relatively specific to certain insect groups. There are three basic types of  biological control strategies; conservation, classical  biological control, and augmentation. These are discussed in more detail below.

Conservation

The conservation of  natural  enemies is probably the most important and readily available  biological control practice available to homeowners and gardeners.  Natural  enemies occur in all areas, from the backyard garden to the commercial field. They are adapted to the local environment and to the target pest, and their conservation is generally simple and cost-effective. Lacewings, lady beetles, hover fly larvae, and parasitized aphid mummies are almost always present in aphid colonies. Fungus-infected adult flies are often common following periods of high humidity. These naturally occurring biological pest controls are often susceptible to the same pesticides used to target their hosts. Preventing the accidental eradication of natural enemies is termed simple conservation.