Sign up to access the complete lesson and track your progress!
Unlock This CourseImagine trying to control garden pests without using any harmful chemicals. That's exactly what biological control does! It's nature's own way of keeping pest populations in check by using living organisms to control other living organisms that we consider pests.
Biological control is a method of controlling pests (insects, weeds, diseases) by using their natural enemies rather than synthetic pesticides. It's like having a natural army that fights crop-damaging pests for us!
Key Definitions:
Traditional pesticides can harm beneficial insects, pollute water sources and create resistant pest populations. Biological control offers a sustainable alternative that works with nature rather than against it. It's safer for humans, animals and the environment whilst being cost-effective in the long term.
There are three main types of organisms used in biological control, each with their own special way of tackling pest problems.
Predators are organisms that hunt and eat their prey. They're like nature's pest control officers, actively seeking out and consuming pest species.
These colourful beetles are aphid-eating machines! A single ladybird can consume up to 50 aphids per day. They're particularly effective in greenhouses and gardens.
Green lacewing larvae are called 'aphid lions' because they're such fierce predators. They use their curved jaws to pierce and suck out the contents of soft-bodied insects.
These tiny arachnids feed on pest mites, thrips and other small insects. They're especially useful in controlling spider mites on crops like strawberries and cucumbers.
These organisms live on or inside their host, eventually killing them. Parasitoids are particularly clever - they lay their eggs inside pest insects and the developing larvae consume the host from the inside.
This tiny wasp is a superhero in greenhouse pest control. It lays its eggs inside whitefly larvae. The developing wasp larva feeds on the whitefly, killing it in the process. The dead whitefly turns black, making it easy for farmers to see that the biological control is working. This method has been used successfully in tomato and cucumber production for over 50 years!
These are disease-causing organisms like bacteria, viruses and fungi that specifically target pest species without harming crops or beneficial insects.
This bacterium produces toxins that are deadly to caterpillars but harmless to humans and other animals. When caterpillars eat crops treated with Bt, the toxin destroys their gut lining, killing them within days. It's widely used to control cabbage white butterfly caterpillars and other leaf-eating pests.
There are three main approaches to implementing biological control, each suited to different situations and pest problems.
This involves introducing a natural enemy from the pest's country of origin. It's like reuniting old enemies! This method is typically used when a pest has been accidentally introduced to a new area without its natural predators.
In the 1920s, prickly pear cactus had taken over millions of hectares of Australian farmland. Scientists introduced the cactus moth from Argentina, whose caterpillars feed exclusively on prickly pear. Within just 10 years, the moth had reduced the cactus population by 99%, turning wasteland back into productive farmland. This remains one of the most spectacular successes in biological control history!
This involves releasing large numbers of natural enemies to boost existing populations or establish new ones. It's like sending in reinforcements to help win the battle against pests.
Many commercial growers regularly release beneficial insects into their greenhouses. For example, they might release thousands of predatory mites to control spider mites on cucumber plants, or introduce parasitic wasps to tackle aphid infestations on tomatoes.
This focuses on protecting and encouraging natural enemies that are already present in the environment. It's about creating the right conditions for beneficial organisms to thrive.
Creating flower strips and hedgerows provides nectar sources for adult beneficial insects and shelter for overwintering populations.
Using selective pesticides or reducing spray frequency helps preserve beneficial insect populations.
Changing crops regularly disrupts pest life cycles whilst maintaining diverse habitats for natural enemies.
Like any pest control method, biological control has both benefits and limitations that farmers need to consider.
Environmentally Safe: No toxic chemicals means no pollution of soil, water, or air.
Target Specific: Natural enemies usually attack only their target pests, leaving beneficial insects unharmed.
Self-Sustaining: Once established, natural enemy populations can maintain themselves.
Cost-Effective: Long-term costs are often lower than repeated pesticide applications.
No Resistance: Pests cannot develop resistance to their natural enemies like they can to chemicals.
Slow Acting: Results may take weeks or months compared to immediate pesticide effects.
Weather Dependent: Temperature and humidity affect the success of biological agents.
Limited Shelf Life: Living organisms cannot be stored like chemical pesticides.
Incomplete Control: May not eliminate 100% of pests, requiring tolerance of some damage.
Initial Costs: Setting up biological control programmes can be expensive.
The most successful approach combines biological control with other sustainable methods in what's called Integrated Pest Management (IPM). This strategy uses biological control as the foundation, supported by cultural practices, resistant crop varieties and minimal pesticide use only when absolutely necessary.
Modern apple growers often use a combination of approaches: they encourage natural predators by planting wildflower strips, use pheromone traps to monitor pest populations, release parasitic wasps to control codling moth and only spray targeted pesticides when pest numbers exceed economic thresholds. This approach has reduced pesticide use by up to 90% in some orchards whilst maintaining high-quality fruit production.
Biological control represents a return to working with nature rather than against it. As we face increasing concerns about pesticide resistance, environmental pollution and food safety, these natural solutions become ever more valuable. The future of sustainable agriculture depends on understanding and harnessing these biological relationships that have existed for millions of years.