Crop Plants: Pest Control (Edexcel IGCSE Science (Double Award))
Revision Note
Crop Plants: Pest Control
Using pest control to increase crop yields
Pests such as insects and other animals can damage crops by eating them
Weeds can outcompete crop plants for space, water and soil nutrients
Fungi can infect crop plants and spread disease which can affect growth and yield
All of these can be controlled by using pesticides (chemical control) or by introducing other species (biological control)
Examples of pesticides include:
Insecticides kill insect pests
Herbicides kill plant pests
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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