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Definition and Scope of Biological Control

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Biological control = the action of parasites, predators or pathogens in maintaining another organism’s population density at a lower average than would occur in their absence

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Applied biological control as “the manipulation of natural enemies by man to control pests”

Natural biological control as that “control that occurs without man’s intervention”

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Advantages of Biological Control:• high level of control at low cost

• self-perpetuating at little cost after initial

effort

• very few harmful effects on man,

environment etc

• some NE’s reproduce rapidly

• some NE’s search out hosts

• some NE’s survive even at low host

densities

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Types of Biological Control:

Classical - involves importation and establishment of new natural enemies to an area, usually for exotic pests, occasionally for natives

Conservation - enhance conditions for existing natural enemy survival and reproduction

Augmentation - involves rearing and release of natural enemies to supplement what is there or when permanent establishment is not possible

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Origins of Pests:

Indigenous (native) - organisms in a specified area that evolved in that location

Adventive (exotic) - organisms in a specified area that did not evolve there, but arrived from somewhere else

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Targets, and Agents of Biological Control

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Targets of biological control:

Insects have been most common target:• worldwide apprx 550 sp •homopterans have been most successful target (due to scale, aphid and whitefly)

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Targets of biological control (cont’d):

Several families of Mites have been targets, including:

Snails are the next most common invertebrate target• either herbivorous sp. that attack crops or• medically important sp. that are intermediate hosts for human or domestic animal pathogens

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Agents of biological control:

Parasitoids have been the most common type of natural enemy introduced for control of insects

• most parasitoids used are in the order Hymenoptera and to a lesser Diptera

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Agents of biological control (cont’d):

Predators are important control agents of both native and introduced pestsThere are 32 families that are significant for pest suppression, of these most common in crops are:• ground beetles• lady beetles• green lacewings • ants

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Agents of biological control (predators cont’d):

SpidersFish (Gambusia affinis) have been used through augmentative releases for the control of mosquito larvae

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Agents of biological control (cont’d):

Pathogens and nematodes attacking arthropods:

• These may be important natural sources of mortality for many species• some have been commercially formulated and marketed as insecticides

These include: • bacteria (esp. genus Bacillus)• viruses (esp. Baculoviridea)• fungi (esp. Entomophthoraceae)• protozoa (including microsporidians)• nematodes (esp Steinernematidae and Heterorhabditidae)