Microbes in Human Welfare — Part 3: Biocontrol agents, biofertilisers and judicious use of antibiotics: visual lesson, CBSE Class 12 Biology

Lesson

Microbes for greener farming

Part 3 — using living organisms instead of chemicals to protect crops and enrich soil, and using antibiotics wisely.

In this lesson you will

Explain biological control of pests and diseases with examples
Name bacterial, fungal and cyanobacterial biofertilisers and how they help
Explain why antibiotics must be used judiciously

Concept

Biological control of pests

Biocontrol uses biological methods to control plant diseases and pests. The organic farmer aims not to eradicate every “pest” but to keep them at manageable levels within a balanced ecosystem.

Table of biocontrol agents and the pests they control
Agent	Controls
Ladybird beetles	Aphids
Dragonflies	Mosquitoes
Bacillus thuringiensis (Bt)	Butterfly caterpillars
Trichoderma (fungus)	Several plant pathogens in the root zone
Baculoviruses (Nucleopolyhedrovirus)	Insects and other arthropods

Concept

Why narrow-spectrum control is better

Baculoviruses are species-specific, narrow-spectrum insecticides with no negative impact on plants, mammals, birds, fish or even non-target insects. They suit integrated pest management (IPM), especially in ecologically sensitive areas.

Table comparing broad-spectrum pesticides with narrow-spectrum biocontrol
	Broad-spectrum chemical pesticide	Narrow-spectrum biocontrol
Targets	Many insects, useful and harmful	Only the pest species
Effect on predators and pollinators	Killed too	Spared
Residues	Toxic residues in soil, water and food	Little or none
Long-term	Pests may return with no natural enemies	Balance maintained

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