Biology · Microbes in Human Welfare · NEET
| Method used | Living organisms and natural predation | Toxic chemical sprays (insecticides) |
| Effect on pests | Kept at manageable levels, not eradicated | Tries to kill pests completely |
| Effect on useful organisms | Useful predators and insects are protected | Kills useful and harmful forms alike |
| Effect on environment | No pollution of soil, water or food | Pollutes soil, ground water, fruits, vegetables |
| Examples | Ladybird, Dragonfly, Bacillus thuringiensis, Trichoderma, Baculovirus | Chemical insecticides, pesticides, weedicides |
No. This is the most common mistake. NCERT clearly says the organic farmer does NOT want to eradicate pests. Pests are kept at manageable levels by natural checks and balances. If all pests were removed, the useful predatory and parasitic insects that feed on them would have no food and would also die. Chemical pesticides, in contrast, try to kill pests indiscriminately.
Chemical insecticides, pesticides and weedicides are toxic and extremely harmful to human beings and animals. They pollute the environment (soil and ground water) and also our fruits, vegetables and crop plants. They kill both useful and harmful life forms without difference, so they destroy the natural balance of the field.
The principle is natural predation. Instead of introduced chemicals, biocontrol relies on the natural feeding relationships in an ecosystem, where one organism (a predator or pathogen) controls the population of the pest. More biodiversity means a more sustainable and self-regulating system.
They are different tools in the same chapter, so students mix them up. Biocontrol agents (ladybird, Bacillus thuringiensis, Trichoderma, Baculovirus) control pests and diseases. Biofertilisers (Rhizobium, Azospirillum, Azotobacter, cyanobacteria) enrich soil nutrients like nitrogen. Biocontrol replaces pesticides; biofertilisers replace chemical fertilisers.
For NEET, treat both as toxic chemicals used in conventional farming. NCERT groups insecticides and pesticides together as harmful chemicals; weedicides are the chemicals used to kill weeds and also pollute soil. Biocontrol aims to reduce our dependence on all of these toxic chemicals.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Biocontrol means using biological methods, that is living organisms like predators, bacteria, fungi or viruses, to control plant diseases and pests instead of using toxic chemicals.
The Ladybird beetle (with red and black markings) is used to get rid of aphids, and Dragonflies are useful to get rid of mosquitoes.
Because biocontrol reduces our dependence on toxic chemicals and pesticides, does not pollute soil and water, and does not kill useful insects, while keeping pests at manageable levels.
No. Organic farming keeps a living, vibrant ecosystem with both predators and pests, because useful predatory and parasitic insects need the pests as food or hosts to survive.
It is from the Class 12 chapter Microbes in Human Welfare, under the topic Microbes as Biocontrol Agents.
