Biological Control Agents (WJEC GCSE Biology)

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Naomi H

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Naomi H

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Biological Control Agents

Biological pest control

  • Biological control agents are living organisms that are used to limit populations of pest species, keeping their numbers to a minimum
  • Biological control organisms include:
    • Predators
    • Parasites
    • Pathogens
  • Biological control allows farmers to reduce reliance on chemical pesticides, which can cause problems with pollution and toxicity in food chains
  • Examples of biological pest control include:
    • Parasitic wasps may lay their eggs inside the bodies of pest species, which then die when the wasp eggs hatch
      • This method was used to save cassava crops from the cassava mealybug pest in South-East Asia
    • A fungal pathogen can be used to infect the larvae of the alfalfa weevil, controlling populations of the pest in environments where the fungus grows
little-parasitic-wasp

Katja Schulz, CC BY 2.0, via Wikimedia Commons

Parasitic wasps are often effective biological control agents due to their highly specific life cycles

Invasive species

  • Invasive species, also known as alien species, are species introduced to regions where they do not naturally occur
    • Humans may introduce a species on purpose, e.g. as a pet or a garden plant
    • Organisms may travel using human transport, e.g. attached to the hull of a ship, resulting in accidental introductions
  • These species can cause problems for native ecosystems in the areas to which they are introduced, e.g.
    • Cane toads were introduced to Australia in the 1930s as a form of biological pest control, causing huge problems for native wildlife
      • The cane toad is toxic to consumers, meaning that it poisons native Australian predators
      • The lack of suitable predators means that cane toad populations have exploded
    • The Asian ladybird was introduced to Europe in the 1990s in an attempt to control aphid populations, but research shows that the species is damaging European ladybird populations
      • The Asian species is more aggressive and will predate on the native species
    • Rhododendron ponticum was introduced to the UK as a garden plant in the 1700s, but has become invasive in native woodlands
      • It grows fast, outcompeting native plant species for light and space
      • Its leaves, when dropped, produce leaf litter that is toxic to many other species
cane-toad rhododendron-ponticum
Bernard Dupont, CC BY-SA 2.0, via Wikimedia Commons Ryan Somma, CC BY-SA 2.0, via Wikimedia Commons

Invasive species, such as cane toads (left) and Rhododendron ponticum (right) can disrupt natural ecosystems; this may be due a lack of effective natural predators or their ability to outcompete native species

Biological control research

  • In order to use effective biological control agents without causing ecological harm, it is essential that new potential agents are properly researched before they are released into non-native environments
    • Proper research may have prevented the problems caused by the introduction of cane toads and Asian ladybirds
  • Scientists around the world need to carry out research trials to assess:
    • The effect of potential control agents on non-target native species
    • The best way to control the agent itself should any non-target effects arise

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Naomi H

Author: Naomi H

Expertise: Biology

Naomi graduated from the University of Oxford with a degree in Biological Sciences. She has 8 years of classroom experience teaching Key Stage 3 up to A-Level biology, and is currently a tutor and A-Level examiner. Naomi especially enjoys creating resources that enable students to build a solid understanding of subject content, while also connecting their knowledge with biology’s exciting, real-world applications.