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Part 4d. Methods of increasing food production and improving sustainability

GCSE level biology exam revision notes on food production

4d. Using biological methods of controlling crop damage from pests - non-chemical methods and their ecological advantages and disadvantages

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Biological methods to control pests

The advantages and disadvantages of using biological methods to control pests

You can deploy other organisms to reduce pest numbers which can act as predators or parasites.

e.g. cane toads were introduced into Australia to eat beetles causing crop damage.

These biological methods can be more sustainable than chemical pesticides, so less harmful to the environment.

They do not involve toxic chemicals that can poison harmless organisms and accumulate in food chains and passed on from one trophic level to the next.

This means less pollution, less risk to people and other wildlife!

BUT, there is often a 'but' e.g. the cane toads are now a 'pest' because they poison native animals that eat them.

Quote from Wikipedia: "The long-term effects of toads on the Australian environment are difficult to determine, however some effects include the depletion of native species that die eating cane toads; the poisoning of pets and humans; depletion of native fauna preyed on by cane toads; and reduced prey populations for native insectivores." - not good!!!

Introducing one organism to control another can lead to unintended consequences.

 

You can control aphids (greenfly and black fly) by employing a predatory insect - can be very effective in the confines of a large greenhouse.

e.g. ladybirds will eat greenfly,

Parasitic wasps can be introduced to control aphid populations that feed on fruit crops - the wasps lay their eggs inside the aphids, which die when the larval wasps hatch out.

The wasp parasites act as a vector' when introduced to control pests e.g. another example is flies laying their eggs on slugs to kill them.

Bacteria can be used to deliberately infect caterpillars with diseases.

BUT, there are always risks in adding another organism to an existing ecosystem, you can never be sure of 'unintended' long term effects!

Some of these biological methods of pest control are used in large scale greenhouses and hydroponics units - these are good methods of 'factory farming' plants - see sections (h) and (i).

Key biology points Source of information are based on the syllabus-specifications for students taking the AQA GCSE, Edexcel GCSE and OCR GCSE level biology examinations (~US grades 9-10).

Further thoughts on biological methods of pest control

Biology Revision Notes – Biological Methods of Pest Control in Agriculture

Biological methods of pest control involve using natural predators, parasites, or pathogens to reduce pest populations without relying on chemical pesticides.

These techniques play a crucial role in sustainable farming, protecting crops while maintaining ecological balance.

1. What Are Biological Pest Control Methods?

Biological pest control uses natural enemies of pests to manage infestations. It is part of Integrated Pest Management (IPM), which combines biological, cultural, and mechanical methods.

Types of Biological Control

  • Predators – Organisms that actively hunt and consume pests (e.g., ladybirds eat aphids).

  • Parasites – Organisms that live on or inside a pest, weakening or killing it (e.g., parasitic wasps target caterpillars).

  • Pathogens – Bacteria, viruses, or fungi that infect and kill pests (e.g., Bacillus thuringiensis bacteria affect caterpillars).

  • Natural Repellents – Companion planting and biological deterrents that prevent pest infestation (e.g., marigolds repel nematodes).

2. Advantages of Biological Pest Control

Using biological methods has several benefits for crop yields, soil fertility, and environmental sustainability.

a) Environmentally Friendly

  • No harmful chemical residues in soil or water.

  • Reduces pollution associated with synthetic pesticides.

b) Target-Specific

  • Biological control agents only affect pests, unlike chemicals that may harm beneficial organisms.

  • Preserves biodiversity, including pollinators such as bees.

c) Improves Soil and Crop Health

  • No chemical build-up in the soil, maintaining long-term fertility.

  • Reduces pesticide resistance, which can develop in pest populations.

d) Cost-Effective in the Long Term

  • Once natural predators establish themselves, they can self-sustain, reducing costs for farmers.

  • Less need for repeated pesticide applications.

e) Supports Organic Farming and Sustainable Food Production

  • Essential for organic agriculture, where synthetic pesticides are prohibited.

  • Helps maintain healthy ecosystems and reduces environmental impact.

3. Disadvantages of Biological Pest Control

Despite its advantages, biological control methods have some challenges.

a) Slower Results

  • Takes time for natural enemies to establish and control pest populations.

  • Less immediate compared to chemical pesticides.

b) Difficult to Control Once Introduced

  • Some biological agents can overpopulate and disrupt ecosystems.

  • Risks of unintended consequences, such as introduced predators targeting beneficial species.

c) May Not Fully Eliminate Pests

  • Reduces pest numbers but may not completely eradicate infestations.

  • Works best in combination with other Integrated Pest Management (IPM) techniques.

d) Requires Careful Planning and Monitoring

  • Must match the right predator to the pest, requiring scientific research.

  • Farmers need knowledge and training to apply biological control effectively.

4. Ecological Advantages and Disadvantages

Ecological Advantages

  • Maintains natural biodiversity and food chains.

  • Reduces reliance on chemical pesticides, which harm ecosystems.

  • Encourages balanced ecosystems, preventing future infestations.

Ecological Disadvantages

  • Introduction of non-native species may disrupt local habitats.

  • Some control agents may outcompete native species, causing ecological imbalance.

  • Effects are hard to reverse if an introduced species spreads uncontrollably.

5. Importance in Global Food Production

Biological pest control plays a vital role in sustainable agriculture to meet food demands while protecting the environment.

  • Reduces crop losses, ensuring higher yields without chemical dependency.

  • Maintains soil fertility, supporting long-term food security.

  • Balances ecosystems, preventing pest outbreaks and ecological harm.

Conclusion

Biological methods offer safe, sustainable solutions for pest control, but they must be carefully managed to avoid unintended consequences.

Combining biological control with crop rotation, companion planting, and careful monitoring ensures effective food production with minimal environmental impact.

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