Crop Plants: Pest Control (Edexcel IGCSE Biology): Revision Note
Exam code: 4BI1
Crop Plants: Pest Control
Using pest control to increase crop yields
Another key way that modern technology has increased food supply is through the use of pesticides
Pesticides are chemicals that kill unwanted species, helping to reduce damage to crops and increase yields by controlling competition from other plants and pests:
Insects and other animals can damage crops by eating them
Weeds compete with crops for space, water, and nutrients.
Fungi can infect crops and spread diseases that reduce growth and yield.
All of these problems can be managed using chemical control (pesticides) or biological control (introducing other species)
Examples of pesticides:
Insecticides – kill insect pests
Herbicides – kill weed species
Fungicides – kill fungal pests
Advantages and disadvantages of pesticides table
Advantages | Disadvantages |
|---|---|
Easily accessible and relatively cheap | Organisms they are meant to kill can develop resistance to them |
Have an immediate effect | They are non-specific chemicals and can often kill other beneficial organisms (e.g., some insecticides might kill bees, which are important pollinators of crops) |
Kills the entire population of pests | They can be persistent chemicals – this means they do not break down in the body and can accumulate in great concentrations at the top of food chains and harm top predators (known as bioaccumulation) |
| Need to be repeatedly applied |
Biological control
Biological control involves using a natural predator to eat the pest species and therefore reduce the impact of the pest on crop yields
This can happen naturally – for example, ladybirds eat aphids
Usually, a species is introduced specifically to prey on the pest species – for example, parasitic wasps can control whitefly in glasshouse tomato crops
As they are based on a predator-prey cycle, they do not completely remove a pest, but keep it at lower levels
Advantages and disadvantages of biological control table
Advantages | Disadvantages |
|---|---|
Natural method - no pollution | May eat other organisms instead of the pest |
No resistance | Takes a longer period of time to be effective |
Can target specific species | Cannot kill entire population - some pests will always be present |
Long lasting | May not adapt to new environment or may move out of the area |
Does not need to be repeatedly applied | May become a pest itself |
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