🐛 Fungal Biopesticides

This lesson builds core elective concepts in BSc Agriculture with practical applications and exam-oriented clarity.

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Fungal Biopesticides

Fungi represent the second most important group of microbial biopesticides after bacteria. They are used both as mycoinsecticides (against insects) and mycofungicides (against plant pathogens). Over 170 products based on entomopathogenic fungi are registered globally.

Trichoderma — The Premier Mycofungicide

Trichoderma species, particularly T. viride, T. harzianum, and T. asperellum, are the most widely used fungal biocontrol agents in India and worldwide.

Modes of Action

• Mycoparasitism — Trichoderma hyphae coil around and penetrate the pathogen's cell wall using enzymes like chitinase, glucanase, and protease
• Antibiosis — production of volatile and non-volatile antibiotics (gliotoxin, viridin, trichodermin)
• Competition — rapid colonization of the rhizosphere, outcompeting pathogens for nutrients and space
• Induced systemic resistance (ISR) — triggers plant defense pathways involving jasmonic acid and ethylene signalling

Target Pathogens

Pathogen	Disease	Crop
Rhizoctonia solani	Sheath blight, damping off	Rice, vegetables
Fusarium oxysporum	Wilt	Tomato, banana, chickpea
Sclerotium rolfsii	Collar rot, stem rot	Groundnut, soybean
Pythium spp.	Damping off	Nursery crops
Macrophomina phaseolina	Charcoal rot	Soybean, sunflower

Application Methods

Trichoderma is applied as seed treatment (4-6 g/kg seed), soil application (2.5 kg/ha mixed with FYM), or seedling dip (10 g/litre). Enrichment with farmyard manure or vermicompost enhances field efficacy.

Beauveria bassiana — The White Muscardine Fungus

Beauveria bassiana is the most widely used entomopathogenic fungus. Conidia (spores) land on the insect cuticle, germinate, penetrate through the exoskeleton using enzymatic and mechanical pressure, and proliferate inside the haemolymph, causing death within 4-7 days. The fungus produces the toxin beauvericin and oosporein, which weaken the insect immune response. It is effective against whiteflies, aphids, thrips, coffee berry borer, and stem borers.

Metarhizium anisopliae — The Green Muscardine Fungus

Metarhizium anisopliae infects insects through a similar cuticular penetration mechanism. It produces destruxins — cyclic depsipeptides that suppress insect immunity. This fungus is particularly effective against soil-dwelling insects such as white grubs, root grubs, termites, and rhinoceros beetle. Commercial products include Met52 and Green Muscle (used for locust control in Africa).

Advantages and Limitations

Fungal biopesticides are advantageous because they can infect insects through contact (no need for ingestion) and persist in the soil. However, they require high humidity (>80% RH) for germination, have slower kill times than chemicals, and demand careful storage at cool temperatures (below 25 degrees C) to maintain spore viability.

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Summary Cheat Sheet

Topic	Key takeaway
Main focus	Fungal Biopesticides — Trichoderma species, Beauveria bassiana, Metarhizium anisopliae, modes of action, and field applications.
Section context	Revise this lesson with the rest of Biopesticides and Biofertilizers for stronger conceptual continuity.