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

4d. Using biological methods to control pests

Doc Brown's Biology exam study revision notes

There are various sections to work through,

after 1 they can be read and studied in any order.

Sub-index of notes on increasing food production

Index of notes on ALL aspects of food production

re-edit 11/05/2023


4(d) You can use biological methods to control pests

(advantages and disadvantages)

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).


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