Q.(a) Organic farmers prefer biological control of diseases and pests to the use of chemicals for the same purpose. Justify.
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Imagine you have a garden. You want your plants to grow strong and healthy, and you also want to keep pests away. There are two main ways to do this: one is with harsh chemicals (chemical fertilizers and pesticides), and the other is with living things or natural substances. Biofertilizers and biopesticides are the second way — they are nature’s own tools for farming.
Let’s start with biofertilizers. Think of them as "living manure." A chemical fertilizer is like giving a plant a direct shot of nutrients — it works fast but can burn the soil over time. A biofertilizer, on the other hand, is a preparation containing live microorganisms (like bacteria, fungi, or algae) that help the plant get nutrients from the soil or air. For example, certain bacteria can take nitrogen from the air and convert it into a form the plant can use. The plant doesn’t get fed directly; instead, the biofertilizer helps the soil become richer and more fertile naturally.
The NCERT textbook (Class 12 Biology, Chapter 10) defines biofertilizers as organisms that enrich the nutrient quality of the soil. The main examples are Rhizobium (a bacterium that lives in root nodules of legumes and fixes nitrogen), Azospirillum and Azotobacter (free-living nitrogen-fixing bacteria), and blue-green algae (like Anabaena) which also fix nitrogen.
Now, biopesticides. These are living organisms or natural substances that control pests — insects, fungi, weeds, etc. — without using synthetic chemicals. Instead of spraying a poison that kills everything (good and bad bugs alike), a biopesticide might use a specific bacterium that only harms a particular caterpillar, or a fungus that attacks a weed. The most famous example is Bacillus thuringiensis (often called Bt), a bacterium that produces a protein toxic to certain insect larvae but harmless to humans, animals, and most other insects.
The key difference between chemical and biological agents: Biofertilizers and biopesticides are renewable, eco-friendly, and do not leave toxic residues in the soil or water. They are a cornerstone of sustainable agriculture — farming that can continue for generations without destroying the land.
Why does this matter for a commerce or humanities student? Because agriculture is not just about biology — it’s about economics, policy, and human health. Chemical fertilizers and pesticides are expensive to produce, can pollute groundwater, and their overuse leads to "superpests" that become resistant. Biofertilizers and biopesticides are often cheaper in the long run, safer for farm workers, and help maintain soil health. Governments around the world (including India) promote them through subsidies and organic farming schemes. Understanding them helps you see why "organic" food costs more, why some farmers switch to natural methods, and how environmental regulations work.
Here’s a quick summary of the main types you should know (from NCERT):
- Biofertilizers:
- Rhizobium (symbiotic with legumes) …
Biocontrol uses living organisms instead of chemicals to manage pests and diseases, an approach favoured in organic farming and described under 'Microbes as Biocontrol Agents' in the NCERT Class 12 Biology chapter on microbes in human welfare. …
(a) Chemicals are toxic and pollute the environment and harm non-target life, whereas biological control is eco-friendly and pest-specific. (b) Bacterium — Bacillus thuringiensis; Fungus — Trichoderma; Insect — Ladybird (beetle).
Concept. Biological control (biocontrol) is the use of biological methods — living organisms — for controlling plant diseases and pests, rather than chemical pesticides, insecticides and herbicides. It is central to organic farming, which stresses a broad ecological understanding of pests and their life cycles.
(a) Why organic farmers prefer biological control.
- Chemical pesticides and herbicides are toxic and extremely harmful — they pollute the soil, water and air.
- They kill non-target and beneficial organisms as well (useful insects, birds, etc.) and can harm humans through residues in food.
- Pests may develop resistance to chemicals, and chemicals leave persistent residues in the environment.
- In contrast, biocontrol agents are eco-friendly, largely pest-specific, do not pollute, and keep the pest population in check as part of a balanced ecosystem — targeting the harmful organism without eradicating everything.
(b) Examples of biocontrol agents. …
- GUJCET 2026Set 051 markMCQQ.Which group of microbes are acting as bio control agents? Select the correct option. (A) Baculo virus, Oscillatoria, Rhizobium (B) Azotobacter, Trichoderma, Glomus (C) Trichoderma, Baculo virus, Bacillus thuringiensis (D) Azospirillum, Anabaena, Bacillus thuringiensis
›Reveal solutionSolution
The all-biocontrol group is Trichoderma, Baculovirus and Bt.
Trichoderma (fungal biocontrol of plant pathogens), Baculoviruses (species-specific insect pathogens) and Bacillus thuringiensis (Bt) (kills caterpillars) are all biological control agents. The other options include N-fixers/cyanobacteria (Rhizobium, Azotobacter, Anaba …
- GSEB Higher Secondary Certificate (HSC) Examination 2026Set ANNUAL1 markMCQQ.Which of the following is an example of cynobacteria?(a) Oscillatoria(b) Spirullina(c) Azospirillum(d) Azotobacter
›Reveal solutionSolution
Oscillatoria is a cyanobacterium (blue-green alga), grouped with Nostoc and Anabaena as autotrophic, nitrogen-fixing biofertilisers, unlike Azospirillum/Azotobacter, which are free-living nitrogen-fixing (but non-photosynthetic) bacteria.
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- GSEB Higher Secondary Certificate (HSC) Examination 2025Set ANNUAL1 markMCQQ.Which of the following is very useful in getting rid of the menace of aphids?(a) Baculovirus(b) Dragonfly(c) Ladybird(d) Trichoderma
›Reveal solutionSolution
The ladybird beetle is a classic biological control agent that preys on aphids.
Biological control uses living organisms to manage pests instead of chemical pesticides. The ladybird beetle (ladybug) is a well-known natural predator of aphids and scale insects, consuming large numbers of them and helping control aphid infestations on crops without chemical intervention. Dragonflies are predators mainly of mosquitoes/small flying insects, Baculovirus is used against lepidopteran/in …
- GSEB Higher Secondary Certificate (HSC) Examination 2025Set ANNUAL1 markMCQQ.Trichoderma is a __________.(a) Symbiotic lichen(b) Free-living bacteria(c) Blue-green algae(d) Free-living fungus
›Reveal solutionSolution
Trichoderma species are free-living fungi found in root ecosystems, used as biocontrol agents against plant pathogens.
Trichoderma is a genus of free-living fungi that are very common in the root ecosystem (rhizosphere). Several species are effective biocontrol agents against a number of plant pathogenic fungi (e.g. Fusarium, Pythium, Rhizoctonia species causing root rot), making …
- GUJCET 2024Set 101 markMCQQ.Which one of the following statement is correct :(i) Baculoviruses are excellent candidates for species specific narrow spectrum insecticidal applications(ii) Bacillus thuringiensis is used to control butterfly caterpillars(iii) Ladybird is useful to get rid of mosquitoes(iv) Trichoderma fungus are used as a biocontrol agents for animal pathogen (A) only (i),(iii) and(iv) (B) only(i) and(ii) (C) only(ii) and(iv) (D) only(iii) and (iv)
›Reveal solutionSolution
(i) and (ii) are correct; ladybird controls aphids and Trichoderma is a biocontrol for plant pathogens.
(i) Baculoviruses are excellent narrow-spectrum, species-specific insecticidal agents — correct. (ii) Bacillus thuringiensis controls butterfly caterpillars — correct. (iii) Ladybird controls aphids, not mosquitoes — wrong. (iv) * …
- GSEB Higher Secondary Certificate (HSC) Examination 2024Set ANNUAL1 markMCQQ.Which fungus is taking part in the formation of mycorrhiza?(a) Mucor(b) Glomus(c) Rhizopus(d) Monuscus
›Reveal solutionSolution
Glomus is the fungal genus most associated with forming mycorrhizae, a mutualistic symbiosis between fungus and plant root that improves the plant's phosphorus uptake.
Mycorrhiza is a symbiotic association between a fungus and the roots of a higher plant; the fungus increases the surface area for absorption and enhances the plant's uptake of phosphorus and water, while receiving photosynthetic carbohydrates from the plant in return. The fungal genus Glomus forms this vesicular-arbuscular mycorrhiza (VAM) association and is exploited as a biofertiliser in …
- GSEB Higher Secondary Certificate (HSC) Examination 2023Set ANNUAL1 markMCQQ.Identify the free-living bacteria which can fix atmospheric nitrogen in the soil.(a) Rhizobium(b) Bt(c) Azospirillum(d) Staphylococci
›Reveal solutionSolution
Free-living nitrogen-fixing soil bacteria include Azospirillum and Azotobacter; Rhizobium fixes nitrogen only in symbiosis with legume roots.
Nitrogen-fixing microbes as biofertilisers:
- Free-living (non-symbiotic) N2-fixers in soil: Azospirillum, Azotobacter.
- Symbiotic N2-fixer: Rhizobium (in root nodules of legumes). …
- GSEB Higher Secondary Certificate (HSC) Examination 2022Set ANNUAL1 markMCQQ.Trichoderma fungus is used for what purpose?(a) To get rid of aphids and mosquitoes(b) In the treatment of diseased plants(c) To control butterfly caterpillars(d) For narrow-spectrum insecticidal purposes
›Reveal solutionSolution
Trichoderma species are free-living fungi found in root ecosystems that act as effective biocontrol agents against several plant pathogenic fungi.
Trichoderma is widely used in biological control of plant diseases: it parasitises and suppresses soil-borne pathogenic fungi (such as Fusarium and Pythium) that cause root-rot and other diseases in plants, offering an eco-friendly alternative to chemical fungicides. This is different from biocontrol agents used against insect pests (like Ba …
- GUJCET 2021Set 151 markMCQQ.As biological-controller, Baculo viruses are pathogens to which organisms? (A) fungi and insects (B) insects and beetles (C) insects and other arthropods (D) beetles and arthropods
›Reveal solutionSolution
Baculoviruses (genus Nucleopolyhedrovirus) attack insects and other arthropods, making them narrow-spectrum biocontrol agents.
Concept. They are species-specific pathogens of insects and other arthropods, useful in integrated pest management. …
- GUJCET 2020Set x1 markMCQQ.Choose the correct option for the statements for Mycorrhiza:(i) It absorbs phosphorus from soli.(ii) It forms root nodules with the association of Rhizobium(iii) They are resistance to root-borne pathogens, tolerance to salinity & drought.(iv) They fix atmospheric nitrogen. (A)(i) and(ii) (B)(i) and(iii) (C) (i),(ii) and(iii) (D)(ii) and (iv)
›Reveal solutionSolution
True for mycorrhiza: (i) absorbs soil phosphorus and (iii) resistance to root pathogens + salinity/drought tolerance → (i) and (iii).
Mycorrhiza is a symbiotic association between a fungus and plant roots.
- (i) TRUE — the fungal partner absorbs phosphorus from soil and passes it to the plant.
- (ii) FALSE — root nodules with Rhizobium are a legume association, not mycorrhiza. …
- GSEB Higher Secondary Certificate (HSC) Examination 2020Set ANNUAL1 markMCQQ.Many members of the genus ________ form mycorrhiza.(a) Saccharomyces(b) Trichoderma(c) Glomus(d) Monascus
›Reveal solutionSolution
Many members of the fungal genus Glomus form mycorrhiza, a mutually beneficial (symbiotic) association with the roots of many plant species, helping the plant absorb phosphorus from the soil.
Mycorrhiza is a symbiotic association between a fungus and the roots (root system) of a higher plant. Species of the fungal genus Glomus form vesicular-arbuscular mycorrhizae (VAM) with the roots of many plants; the fungus absorbs phosphorus from soil and passes it on to the plant, while in turn benefiting from the plant's photosynthates. Plants with such mycorrhizal associations also show resistance to root-borne pathogens and tolera …
- GSEB Higher Secondary Certificate (HSC) Examination 2020Set ANNUAL1 markMCQQ.The Lady bird and Dragonflies are useful to get rid of(a) Aphids and mosquitoes(b) Aphids and rotifers(c) Housefly and Mosquitoes(d) Cockroach and Locust
›Reveal solutionSolution
Ladybird beetles are effective biocontrol agents against aphids, while dragonflies are effective predators of mosquitoes, both used to reduce pest populations without chemical pesticides.
Biological control uses natural predators/parasites to keep pest populations in check without relying on chemical pesticides. The ladybird (ladybird beetle) is a well-known predator of aphids, which are common plant pests that damage crops by sucking sap. Dragonflies are natural predators of mosquitoes (they cons …
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