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examBoard: Pearson Edexcel
examType: IGCSE
lessonTitle: Pest Control Methods
Pests are organisms that damage crops, reducing yield and quality. They include insects, weeds, fungi, bacteria and rodents. Effective pest control is essential for ensuring food security and maximising agricultural productivity.
Key Definitions:
Pests can reduce crop yields by 30-40% globally. They damage crops by eating plant tissues, spreading diseases, competing for nutrients and contaminating harvested products. Without effective pest control, global food production would be severely compromised, especially as the world population continues to grow.
Modern pest control aims to balance effectiveness with environmental protection. Sustainable approaches seek to minimise harm to beneficial organisms, prevent pest resistance and reduce pollution while maintaining crop productivity.
Biological control uses living organisms to suppress pest populations. It works with natural ecological relationships rather than against them.
There are several approaches to biological pest control, each using different mechanisms to reduce pest populations:
Introducing predatory insects like ladybirds to feed on aphids. For example, releasing lacewing larvae to control whitefly populations in greenhouses.
Insects that lay eggs in or on pest species. The parasitoid larvae develop by feeding on the host, eventually killing it. Trichogramma wasps are used to control caterpillar pests.
Microorganisms that cause disease in pests. Bacillus thuringiensis (Bt) bacteria produce proteins toxic to certain insect larvae but harmless to humans.
One of the most successful biological control programmes involved the cactus moth (Cactoblastis cactorum) to control prickly pear cactus in Australia. In the 1920s, prickly pear had invaded over 60 million acres of land. The introduction of the cactus moth, whose larvae feed exclusively on prickly pear, brought the infestation under control within a few years. This case demonstrates how highly specific biological control agents can effectively manage pest populations with minimal environmental impact.
Chemical control involves using synthetic or natural substances to kill, repel, or regulate pest growth. It remains the most widely used approach in conventional agriculture.
Different chemical compounds target specific types of pests:
Target insect pests. Examples include pyrethroids, organophosphates and neonicotinoids. They work by disrupting the nervous system or other vital functions of insects.
Control unwanted plants (weeds). Glyphosate is a widely used broad-spectrum herbicide that inhibits an enzyme pathway essential for plant growth.
Combat fungal diseases. Copper-based compounds and sulfur are used to prevent fungal spores from germinating or penetrating plant tissues.
DDT was once considered a miracle insecticide, widely used after World War II. However, its widespread use led to insect resistance and severe environmental impacts, including bioaccumulation in food chains and harmful effects on bird populations by thinning eggshells. This case illustrates the dangers of overreliance on chemical controls and the importance of understanding long-term ecological consequences. DDT was banned in the UK in 1984 and globally for agricultural use under the Stockholm Convention in 2004.
These methods involve physical barriers, traps, or modifications to farming practices to reduce pest populations or prevent damage.
IPM combines multiple pest control strategies in a coordinated approach to minimise economic, health and environmental risks. It represents the most sustainable approach to pest management in modern agriculture.
IPM follows a systematic approach to pest management:
UK apple growers have successfully implemented IPM to control codling moth, a major apple pest. The programme includes pheromone traps to monitor moth populations, timing sprays based on temperature models that predict moth development, releasing parasitic wasps and using mating disruption techniques. This approach has reduced pesticide use by up to 60% while maintaining fruit quality. The success demonstrates how combining multiple strategies can achieve better results than relying on a single method.
Pest control continues to evolve with new technologies and approaches being developed to address challenges in food production while minimising environmental impact.
Effective pest control requires understanding the pest's biology, the crop's requirements and the environmental context. The most sustainable approaches typically:
By applying these principles, farmers can protect their crops while contributing to sustainable food production systems that will feed the growing global population.
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