Brainlag PlusEdexcel (Biology only): controlling pests with living organisms and weighing it against pesticides; and how persistent pesticides build up along food chains, with the calculations data questions ask for.
Biological control (Edexcel, Biology only)
Biological control uses a living organism, such as a predator, parasite or pathogen, to reduce the numbers of a pest.
Ladybirds eat aphids; tiny wasps lay their eggs inside whitefly larvae in greenhouses; nematode worms infect slugs.
| Biological control | Chemical pesticide | |
|---|---|---|
| speed | slow to take effect | fast |
| other species | usually targets one pest, but may harm others | often kills useful species too |
| residues | none | can remain on food and build up in food chains |
| repeat use | the agent breeds, so it keeps working | must be sprayed again; pests can become resistant |
Biological control rarely wipes the pest out: when the pest is rare, the control organism has less food, so its numbers fall too. And it can go badly wrong. Cane toads were brought to Australia to eat beetles in sugar cane; they ate many other animals, spread widely and poisoned native predators that ate them.
Edexcel also asks you to compare biological control with fertilisers, which add mineral ions such as nitrates so crops grow faster; they do not control pests.
In an example, the control agent is the organism doing the controlling; the pest is what it eats or infects.
The rest of this lesson and its 10 practice questions are in Plus.
Screen 1 of 3, free to read.
- 10 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards