🐞 Biological Control Methods
Biological method history, predators, parasitoids, Trichogramma, microbial control (NPV, Bt, fungi, EPN), HPR, legislative measures for CUET Agriculture
4. Biological Method (जैविक विधि)
Ladybird Beetle (Coccinella) — most exploited predator for aphid control — Source: Wikimedia Commons (CC)
Biological control is the use of living organisms (natural enemies) to suppress pest populations below damaging levels. The term was first used by Smith in the context of insect pest management. This method is environmentally friendly, self-sustaining, and a cornerstone of IPM.
Key Historical Milestones
- 1762 — First biological control: Indian Mynah birds were introduced in Mauritius to control the Red Locust — the earliest recorded deliberate use of one organism to control another
- 1888 — Rodolia cardinalis (Vedalia beetle) was imported from Australia to California, USA to control the Cottony cushion scale (Icerya purchasi) on citrus — this is considered the first classical biological control success and proved that importing natural enemies could work spectacularly
- C.V. Riley is recognised as the "Father of Biological Control" for his pioneering work in establishing the scientific basis of using natural enemies
- In England: Aphelinus mali was used to control Woolly aphid on apple; Eretmocerus serius was used against Icerya
Principles of Biological Control
Biological control operates on three fundamental principles:
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4. Biological Method (जैविक विधि)
Ladybird Beetle (Coccinella) — most exploited predator for aphid control — Source: Wikimedia Commons (CC)
Biological control is the use of living organisms (natural enemies) to suppress pest populations below damaging levels. The term was first used by Smith in the context of insect pest management. This method is environmentally friendly, self-sustaining, and a cornerstone of IPM.
Key Historical Milestones
- 1762 — First biological control: Indian Mynah birds were introduced in Mauritius to control the Red Locust — the earliest recorded deliberate use of one organism to control another
- 1888 — Rodolia cardinalis (Vedalia beetle) was imported from Australia to California, USA to control the Cottony cushion scale (Icerya purchasi) on citrus — this is considered the first classical biological control success and proved that importing natural enemies could work spectacularly
- C.V. Riley is recognised as the "Father of Biological Control" for his pioneering work in establishing the scientific basis of using natural enemies
- In England: Aphelinus mali was used to control Woolly aphid on apple; Eretmocerus serius was used against Icerya
Principles of Biological Control
Biological control operates on three fundamental principles:
- Introduction (प्रवेशन) — Importing a natural enemy from the pest's area of origin (classical biological control). The idea is that pests often arrive in new areas without their natural enemies.
- Augmentation (संवर्धन) — Mass rearing bioagents in laboratories and making periodic releases into the field to boost their numbers beyond what occurs naturally.
- Conservation (संरक्षण) — Protecting and enhancing existing natural enemies already present in the field by providing shelter, avoiding broad-spectrum pesticides, and maintaining habitat diversity.
Natural Enemies / Bioagents
A. Predators (परभक्षी)
Predators are free-living organisms that actively hunt and feed on multiple prey individuals during their lifetime. They are typically larger than or similar in size to their prey. The main insect orders that contain important predators are Coleoptera, Diptera, and Neuroptera.
| S.No. | Predator Insect | Host/Prey |
|---|---|---|
| 1. | Lady bird beetle (Coccinella sp.) — Coleoptera | Aphids; Coccinella septempunctata (seven-spotted ladybird) is the most important species |
| 2. | Syrphid fly (Syrphis sp.) — Diptera | Aphids — the larvae of syrphid flies are voracious aphid feeders |
| 3. | Chrysopa (Aphid lion / Green lacewing) — Neuroptera | Aphids, Thrips — the larval stage is called "aphid lion" due to its fierce predatory behaviour |
| 4. | Praying mantis (Mantis sp.) — Mantodea | Aphids, Jassids, small insects — a generalist predator with distinctive raptorial forelegs |
| 5. | Dragon fly (Aeshna sp.) — Odonata | Flies, Mosquitoes — an aerial predator that catches prey in flight |
Additional Predator-Prey Relationships
| S.No. | Predator | Host |
|---|---|---|
| 1. | Vedalia beetle, R. cardinalis (Coleoptera) | Cottony cushion scale |
| 2. | Coccinella sp., Chrysoperla carnea (Neuroptera) | Aphids |
| 3. | Phytoseiulus sp. & Amblyseius sp. (Acari) | Phytophagous mites |
| 4. | Big eyed bug, Geocoris (Hemiptera) | Caterpillars |
IMPORTANT
The most exploited indigenous predator in India is Cryptolaemus montrouzieri (किप्टोलेमस मोनट्रोजीरी) — it is widely reared and released for mealybug control in orchards, vineyards, and coffee plantations across the country.
B. Parasitoids (परजीव्याभ)
Parasitoids differ from predators in that they are smaller than their hosts, live on or inside a single host individual, and eventually kill the host as they complete their development. Most parasitoids belong to the orders Hymenoptera (wasps) and Diptera (flies). They are classified by the host stage they attack:
| S.No. | Parasitoid | Host Pest | Type |
|---|---|---|---|
| 1. | Trichogramma sp. | Stem borer (Rice), Bollworm (Cotton) | Egg parasitoid — lays its eggs inside the pest's eggs |
| 2. | Telenomus remus | Tobacco caterpillar | Egg parasitoid |
| 3. | Evania appendigaster | Cockroach ootheca | Egg parasitoid |
| 4. | Chelonus blackburni | Several lepidopterous pests | Egg-larval parasitoid — enters egg, completes development in larva |
| 5. | Copidosoma koehleri | Potato tuber moth | Egg-larval parasitoid |
| 6. | Campolestis chloridae | Helicoverpa armigera | Larval parasitoid |
| 7. | Bracon sp. | Coconut black-headed caterpillar | Larval parasitoid |
| 8. | Cotesia plutellae | DBM (Diamond Back Moth) | Larval parasitoid |
| 9. | Isotima javensis | Sugarcane shoot borer | Larval-pupal parasitoid |
| 10. | Brachymeria nephantidis | Coconut black-headed caterpillar | Pupal parasitoid |
| 11. | Aphelinus mali | Apple woolly aphid | Nymphal and adult parasitoid |
| 12. | Epiricania melanoleuca | Pyrilla of sugarcane | Parasitoid |
Trichogramma Release Schedule
Trichogramma is the most widely used egg parasitoid worldwide. These tiny wasps (less than 1 mm) lay their eggs inside the eggs of pest moths, killing the pest before it can hatch and damage crops. Different species of Trichogramma are matched to specific crops and pests:
| Crop | Parasitoid Species | Target Pest | Dosage/ha | No. of Releases |
|---|---|---|---|---|
| Paddy | T. japonicum | Stem borer | 50,000 | 6 |
| Tomato | T. pretiosum | Fruit borer | 50,000 | 6 |
| Cole crops | T. brassicae | DBM | 100,000 | 6 |
| Tobacco | Trichogramma sp. | Spodoptera litura | 100,000 | 3-4 |
| Sugarcane | Trichogramma sp. | Sugarcane borer | 50,000 | 4-6 |
| Cotton | Trichogramma sp. | H. armigera | 150,000 | 6 |
| Maize | Trichogramma sp. | Chilo partellus | 100,000 | 3 |
5. Microbial Method (सूक्षमजीवी विधि)
The microbial method uses microorganisms — viruses, bacteria, fungi, nematodes, and protozoa — that naturally cause disease in insects, thereby controlling their populations. The term "Microbial Control" was coined by Steinhaus in 1949. Agostina Bassi is known as the "Father of Insect Pathology" for his foundational work demonstrating that microorganisms can cause disease in insects.
i. Virus (विषाणु)
Insect-pathogenic viruses are highly host-specific, meaning they attack only their target pest without harming beneficial insects, humans, or other animals.
Symptoms of virus infection in insects:
- Insect becomes sluggish and stops feeding; body turns pale/yellow
- Body swells up; cuticle becomes fragile and easily ruptured
- Body fluids (haemolymph) leak out; body shrinks
- Dead insect typically hangs from upper plant parts; body turns black — a characteristic sign of viral infection
a. NPV (Nuclear Polyhedrosis Virus):
NPV is the most important group of insect viruses used in pest management:
- HaNPV = targets Helicoverpa armigera (gram pod borer) → applied @ 500 LE (Larval Equivalents) per hectare
- SlNPV = targets Spodoptera litura → applied on tobacco and cotton
- Commercial products include: Biovirus-H, Virin-EG, Helicidal etc.
- Application rates: Helicoverpa on cotton → 500 LE/hectare; on gram/chickpea → 250 LE/hectare
b. CPV (Cytoplasmic Polyhedrosis Virus): Used against Helicoverpa armigera
c. GV (Granulosis Virus): Another group of insect-specific viruses
ii. Bacteria (जीवाणु)
a. Bt: Bacillus thuringiensis
Bt is the most important and widely used biopesticide in the world. It produces crystal proteins (Cry proteins) during sporulation that are toxic to insect larvae when ingested. The toxin dissolves in the alkaline gut of caterpillars, binds to gut receptors, creates pores in the gut wall, and causes the larva to stop feeding and die.
Commercial Bt products include: Halt, Delfin, Biovit, Bioylep, Dipel, Thuricide etc.
Cry genes and their target insect orders:
| Cry Gene | Toxic to Insect Order |
|---|---|
| Cry I | Lepidoptera (moths and butterflies) |
| Cry II | Lepidoptera, Diptera |
| Cry III | Coleoptera (beetles) |
| Cry IV | Diptera (flies) |
| Cry V | Lepidoptera, Coleoptera |
IMPORTANT
Bt cotton varieties in India:
- Bollgard-I: Contains the Cry 1Ac gene — provides protection against Helicoverpa armigera
- Bollgard-II: Contains Cry 1Ac + Cry 2Ab genes — provides broader and more durable resistance
b. Bacillus popillae: Controls white grub (Japanese beetle) by causing milky disease — the bacteria multiply in the grub's haemolymph, turning it milky white, and eventually killing the grub.
iii. Fungi (कवक/फफूंद)
Entomopathogenic fungi infect insects by penetrating through the cuticle (body wall), unlike bacteria and viruses that must be ingested. This makes them effective against sucking pests too.
| Fungus | Target | Product |
|---|---|---|
| Beauveria bassiana | White grub, various insects | Biobeauverine |
| Metarhizium anisopliae | White grub, termite, Pyrilla | Metaquino; Bayo (commercial name) |
| Verticillium lecanii | Coffee green scale | — |
| Trichoderma | Soil-borne fungal pathogens | Soil application @ 6-8 gm/kg seed |
iv. Nematode (सूत्रकृमि) — EPN (Entomopathogenic Nematode)
Entomopathogenic nematodes (EPNs) are microscopic roundworms that kill insects by entering through natural openings and releasing symbiotic bacteria into the host's body. The bacteria multiply rapidly, causing septicaemia (blood poisoning) that kills the insect within 24-48 hours.
- DD-136: Neoaplectana carpocapsae carries the bacterium Achromobacter nematophilus → Controls Codling moth (Cydia pomonella)
| S.No. | EPN Name | Symbiotic Bacteria | Target Pest |
|---|---|---|---|
| 1. | Steinernema carpocapsae | Xenorhabdus sp. | White grub |
| 2. | Heterorhabditis sp. | Photorhabdus sp. | White grub |
v. Protozoa
- Farinocystis tribolii — used against Red flour beetle in stored grain
6. Host Plant Resistance (HPR) (पोषक पादप प्रतिरोधी)
Host Plant Resistance (HPR) is the use of crop varieties that are inherently resistant to pest attack, either through physical barriers (thick cuticle, trichomes) or chemical defences (toxic or repellent compounds).
- The concept was formalised by R.H. Painter (1951), who is known as the "Father of HPR"
- J.N. Heavens (1792): First reported that the wheat variety "Underhill" was resistant to the Hessian fly (Mayetiola destructor) — this is the earliest recorded observation of host plant resistance
- The most successful example of HPR in history: Grape phylloxera control — European grapevines were grafted onto phylloxera-resistant American rootstocks, saving the entire European wine industry
Three Mechanisms of HPR (Painter's Classification)
- Antibiosis — The plant produces substances that are toxic or harmful to the pest, affecting its survival, growth, or reproduction
- Antixenosis (Non-preference) — The plant has features that make it unattractive to the pest for feeding, oviposition, or shelter
- Tolerance — The plant can withstand or recover from pest damage without significant yield loss, even though the pest feeds normally
7. Legislative Measures (वैध/कानूनी विधि)
Legislative measures use laws and regulations to prevent the introduction and spread of pests.
- Plant Quarantine — A system of inspections and regulations that prevents the entry of foreign pests into a country or region through trade or travel
- Foreign Quarantine: Enforced at international borders to prevent exotic pests from entering
- Domestic Quarantine: Enforced within the country to prevent spread of localised pests — for example, the San Jose Scale quarantine in India restricts movement of infested plant material
- Phytosanitary Certificate: An official document required for international plant movement, certifying that the plant material is free from regulated pests
- Mango pest with quarantine importance: Stone/Nut weevil — its presence in India restricts mango exports to certain countries
Key Points for CUET
IMPORTANT
- C.V. Riley = Father of Biological Control
- Steinhaus (1949) coined "Microbial Control"
- R.H. Painter (1951) = Father of Host Plant Resistance
- Bt (Bacillus thuringiensis) — most important biopesticide; Cry genes target different insect orders
- Trichogramma — most widely used egg parasitoid worldwide
- Cryptolaemus montrouzieri — most exploited indigenous predator in India (for mealybug)
- HaNPV — Helicoverpa-specific nuclear polyhedrosis virus; 500 LE/ha
- Bollgard-I: Cry1Ac; Bollgard-II: Cry1Ac + Cry2Ab
- First biological control success (1888): Vedalia beetle vs. Cottony cushion scale
- Plant quarantine prevents introduction of foreign pests
Summary Cheat Sheet
| Concept / Topic | Key Details / Explanation |
|---|---|
| Biological control | Use of living organisms (natural enemies) to suppress pests; term first used by Smith |
| First biological control | 1762 — Indian Mynah birds introduced in Mauritius for Red Locust |
| First classical success | 1888 — Vedalia beetle (Rodolia cardinalis) from Australia to California for Cottony cushion scale |
| Father of Biological Control | C.V. Riley |
| 3 principles | Introduction (import natural enemy), Augmentation (mass rear + release), Conservation (protect existing enemies) |
| Predators vs Parasitoids | Predators: larger, free-living, eat multiple prey Parasitoids: smaller, develop on/inside single host, kill it |
| Key predators | Coccinella (ladybird) → aphids; Chrysopa (aphid lion) → aphids/thrips; Syrphid fly → aphids; Praying mantis → various |
| Most exploited indigenous predator (India) | Cryptolaemus montrouzieri → mealybug control |
| Most widely used egg parasitoid | Trichogramma sp. — lays eggs inside pest eggs |
| Trichogramma — Paddy | T. japonicum; 50,000/ha; 6 releases; targets stem borer |
| Trichogramma — Cotton | Trichogramma sp.; 150,000/ha; 6 releases; targets H. armigera |
| Microbial control coined by | Steinhaus (1949) |
| Father of Insect Pathology | Agostina Bassi |
| NPV — HaNPV | Targets Helicoverpa armigera; dose 500 LE/ha |
| Bt (Bacillus thuringiensis) | Most important biopesticide; Cry proteins toxic to larvae |
| Cry I gene | Toxic to Lepidoptera |
| Cry III gene | Toxic to Coleoptera |
| Bollgard-I | Cry 1Ac gene |
| Bollgard-II | Cry 1Ac + Cry 2Ab genes |
| Bacillus popillae | Controls white grub; causes milky disease |
| Entomopathogenic fungi | Beauveria bassiana & Metarhizium anisopliae → white grub, termite; penetrate through cuticle |
| EPN (Entomopathogenic Nematodes) | Kill insects via symbiotic bacteria causing septicaemia in 24-48 hrs |
| Steinernema | Symbiont: Xenorhabdus; targets white grub |
| Heterorhabditis | Symbiont: Photorhabdus; targets white grub |
| Father of HPR | R.H. Painter (1951) |
| HPR mechanisms (Painter) | Antibiosis (toxic to pest), Antixenosis (unattractive to pest), Tolerance (withstands damage) |
| First HPR observation | J.N. Heavens (1792) — wheat "Underhill" resistant to Hessian fly |
| Most famous HPR success | Grape phylloxera — European vines grafted on American rootstocks |
| Plant quarantine | Prevents entry of foreign pests; Phytosanitary Certificate required for international plant movement |
| Quarantine pest — Mango | Stone/Nut weevil restricts mango exports |
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