Definition and Scope of Biological Control - PowerPoint PPT Presentation

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Definition and Scope of Biological Control
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Definition and Scope of Biological Control

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  1. Definition and Scope of Biological Control

  2. 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

  3. 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”

  4. 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

  5. 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

  6. 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

  7. Targets, and Agents of Biological Control

  8. 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)

  9. 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

  10. 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

  11. Agents of biological control (cont’d): • Predators are important control agents of both native and introduced pests • There are 32 families that are significant for pest suppression, of these most common in crops are: • ground beetles • lady beetles • green lacewings • ants

  12. Agents of biological control (predators cont’d): Spiders Fish (Gambusia affinis) have been used through augmentative releases for the control of mosquito larvae

  13. 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)