Maarg Manthan · Topic 2.8

Biological Control

Environment & Ecology › Ecosystem Structure and Function · Topic 2.8

Biological control is the use of living organisms, such as predators, parasitoids, pathogens and competitors, to suppress populations of pests, weeds or disease vectors, instead of or along with chemical pesticides. It is a main part of integrated pest management. The three main approaches are classical biological control, in which natural enemies from the pest's home region are introduced to control an invasive pest; augmentation, where natural enemies are mass-reared and released; and conservation, where the habitat is managed to support existing natural enemies. Examples include ladybird beetles against aphids and scale insects, Trichogramma wasps against borers, Bacillus thuringiensis against caterpillars, Gambusia fish against mosquito larvae, and the cochineal insect against the prickly pear in Australia. Its advantages are specificity, lower pollution and lasting effect, and its risks include non-target damage.

5 min read · UPSC Prelims · Environment & Ecology · Ecosystem Structure and Function

At a Glance

Idea Use natural enemies
Classical Introduce from home region
Examples Ladybird, Trichogramma, Bt
Fish for mosquitoes Gambusia
Risk Non-target effects
Exam link UPSC Prelims, Environment & Ecology: Ecosystem Structure and Function

Where Does It Fit?

This is the last topic of the macro on ecosystem structure and function. It applies the ideas of food chains and species interactions to practical pest management, and it connects ecology with agriculture and public health. Previous topic: Biomagnification. Next topic: Types of Species.

What Are the Methods and Agents of Biological Control?

Method or agent	Details and examples
Classical biological control	Importing natural enemies from the native region of an invasive pest. Example: the cochineal insect Dactylopius against prickly pear in Australia and India; the beetle Cyrtobagous against water fern Salvinia
Augmentation	Mass rearing and releasing natural enemies, such as Trichogramma egg parasitoids against sugarcane and cotton borers
Conservation	Protecting habitats, hedgerows and flowering plants to support natural enemies
Predators	Ladybird beetles on aphids, lacewings, spiders and birds
Parasitoids	Insects such as wasps that lay eggs in a host and kill it, like Trichogramma and Cotesia
Pathogens	Bacillus thuringiensis (Bt) toxin, the fungus Beauveria bassiana, nuclear polyhedrosis virus (NPV) and Trichoderma against soil fungi
Fish and other agents	Gambusia and Poecilia fish eat mosquito larvae; ducks eat snails and weeds in rice fields

What Are the Benefits, Risks and Indian Context?

Benefits: target specific, lower residues, reduced biomagnification and resistance, lower cost in the long run, and safer for farm workers
Integrated pest management: combines biological, cultural and mechanical controls with minimum chemicals
Risks: agents may attack non-target species or become invasive; the cane toad introduced into Australia in 1935 to control beetles became a destructive pest
Slow action: biological control often works slower than chemicals
Pest resurgence: pesticides kill natural enemies and cause outbreaks
Indian institutions: National Bureau of Agricultural Insect Resources, Bengaluru, and the Directorate of Plant Protection, Quarantine and Storage
Biopesticides: neem products, Bt and NPV are registered under the Insecticides Act, 1968
Bt cotton link: Bt toxin genes are put into cotton, a genetic form of the same idea

What Else Should You Remember?

Trichocards: cards with parasitoid eggs used by farmers
Pheromone traps: use insect sex chemicals to trap or confuse pests
Sterile insect technique: release of sterilised male insects to reduce breeding
Weed control: Zygogramma beetle against Parthenium
Water hyacinth: Neochetina weevils reduce this weed in Indian lakes
Mosquito control: Bti bacteria, Gambusia fish and the Wolbachia method
Wolbachia: bacteria that reduce the ability of mosquitoes to spread dengue
Genetically modified mosquito: an approach in some trials
Beneficial insects: honey bees, silkworms and earthworms are useful species
Natural farming: uses cow-based inputs and natural enemies
Organic farming: India’s Paramparagat Krishi Vikas Yojana supports it
Pesticide poisoning: Punjab and Kerala cases led to the Endosulfan ban in 2011
Pesticide residues: food safety standards limit residues
Resistance: pests evolve resistance to chemicals
Regulation: imported biocontrol agents need quarantine checks
Island effect: agents introduced to islands often harm native species
Link: toxins in food chains are in Biomagnification
Link to species: invasive species are in Endemic Species, Keystone Species, Indicator Species, Invasive Species
Seed treatment: coating seeds with Trichoderma protects them from soil fungi
Banker plants: plants that host natural enemies near crops
Biocontrol of locusts: fungal agents are being tested against locust swarms
Quarantine rules: import of live organisms requires approval, to prevent new pests
Cost and training: farmers need training and supply systems for natural enemies
Success story: a parasitoid wasp imported and released in Tamil Nadu helped to control the papaya mealybug, a case often cited in India
Parthenium control: the Mexican beetle Zygogramma bicolorata was released in India to reduce Parthenium, a weed that causes allergies
Predatory birds: owls and kites eat rodents in fields, and owl boxes are used in some farms
Resistance management: rotating methods slows resistance
Farm biodiversity: hedgerows and flowering borders raise numbers of natural enemies

Why Does It Matter for the Exam?

Methods: classical, augmentation, conservation
Agents: Trichogramma, Bt, Gambusia
Risks: cane toad
Current affairs link: biopesticides and Wolbachia
Common errors: calling Bt cotton a biological control agent or saying it has no risks

As an analytical point, biological control reduces dependence on chemicals and avoids biomagnification, but introductions must be tested for safety. Integrated pest management that mixes methods is the practical path.

Why Is This Topic Important?

Methods Three
Agents Predators, pathogens
Risks Non-target

What Came Next?

The next macro covers population ecology and species interactions, beginning with types of species. Next topic: Types of Species.

Key People and Terms

Biocontrol Use of natural enemies
IPM Integrated pest management
Parasitoid Insect that kills its host
Biopesticide Natural pest killer
Pheromone Chemical signal
Augmentation Release of mass-reared enemies

Exam Corner

Points to Remember

Trichogramma attacks eggs of borers.
Gambusia eats mosquito larvae.
Bt is a bacterium.
Cane toad introduced 1935 in Australia.
Endosulfan banned in India in 2011.

Do Not Confuse With

Biological control and biopesticide Living enemy versus product of living origin
Predator and parasitoid Eats prey versus lays eggs and kills host
Classical and augmentation Introduce once versus mass release

Memory Hook

Ladybird for aphids, Trichogramma for borers, Gambusia for larvae, Bt for caterpillars.

Mains Angle

Questions ask for examples and the risks. These points help.

Concept Natural enemies
IPM Combined methods
Risks Introductions

A Question You May Face

An original practice question, not a past paper question.

“What is biological control? Discuss its methods, advantages and the risks involved with examples.”

How to Answer

Define Biocontrol.
Methods Three.
Benefits Safer.
Risks Cane toad.

GS Relevance

Prelims: examples of agents, advantages and risks, IPM. GS Paper 3: agriculture, ecology.

Frequently Asked Questions

What is biological control?

Biological control is the use of living organisms such as predators, parasitoids, pathogens and competitors to reduce the numbers of pests, weeds or disease vectors. It is a main component of integrated pest management and reduces the use of harmful chemical pesticides in agriculture and public health.

What are the main methods of biological control?

The three main methods are classical biological control, which introduces natural enemies from the pest's native region, augmentation, in which natural enemies are mass-reared and released, and conservation, in which habitats and farming practices are managed to protect and increase the natural enemies already present.

Give examples of biological control agents.

Examples include ladybird beetles that feed on aphids, Trichogramma wasps that parasitise the eggs of borers, Bacillus thuringiensis bacteria that kill caterpillars, Gambusia fish that eat mosquito larvae, the fungus Beauveria bassiana, and the cochineal insect used against prickly pear.

What are the risks of biological control?

The risks include harm to non-target species, because a control agent may attack harmless native species, and the chance that the agent itself becomes invasive. The cane toad, introduced in Australia in 1935 to control beetles in sugarcane, became a major pest that poisons native predators.

What is integrated pest management?

Integrated pest management is a strategy that combines biological control, resistant crop varieties, crop rotation, traps, mechanical methods and minimal, targeted use of pesticides to keep pests below damaging levels. It aims to be economical and safe for people, wildlife and the environment.

PYQ Practice — Statement Analysis

1 Trichogramma is a parasitoid used for biological control.

True

Against borers.

2 The cane toad was a successful and risk-free biocontrol agent.

False

It became a pest.

3 Gambusia fish are used to control mosquito larvae.