Green Muscardine Fungus
Metarhizium anisopliae
📖 Description
Metarhizium anisopliae (formerly Metarhizium anisopliae var. anisopliae) is one of the most commercially important entomopathogenic fungi (EPF) in Indian agriculture and the most widely deployed biocontrol fungus against coconut rhinoceros beetle, sugarcane white grub, and coffee berry borer. The species has a broad host range (>200 insect species across 7 orders) and an extremely well-characterised infection cycle: conidia attach to the insect cuticle, germinate in response to cuticular lipids and humidity, penetrate the cuticle using specialised appressoria and penetration pegs, proliferate in the haemocoel as yeast-like blastospores that produce toxins (destruxins), kill the host within 5–10 days, and then sporulate on the cadaver surface to produce the diagnostic olive-green mould that gives the disease its common name ‘green muscardine’. M. anisopliae is mass-reared by several Indian biocontrol laboratories (NBAIR Bengaluru, IIHR Bengaluru, ICAR-CPCRI Kasaragod) on rice grain or liquid fermentation, formulated as wettable powder, oil dispersion, or granules, and applied against rhinoceros beetle in coconut (palm-base application), white grubs in sugarcane and groundnut (soil drench), rice stem borer (foliar spray), coffee berry borer (spray), termites (soil drench), and mosquito larvae (water surface application). Estimated value of biological control services provided by M. anisopliae and related EPF (Beauveria bassiana, Lecanicillium lecanii) in Indian agriculture exceeds ₹2,000 crore per year.
⚠️ Symptoms to watch for
- No plant damage — this is a beneficial biocontrol fungus. Visible mortality of target insects within 5–10 days of application, characteristic olive-green to dark green velvety mould on the surface of infected cadavers (diagnostic), flaccid and mummified cadavers found attached to plant surfaces or in soil, and reduced adult emergence of target pests in subsequent weeks. The fungus does not infect plants, mammals, fish, or non-target beneficial insects — making it one of the safest biocontrol agents available.
🩹 Treatment
- No treatment needed — this is a beneficial biocontrol fungus. Apply commercially reared conidial formulations (wettable powder, oil dispersion, granular) at 1×10^12–1×10^13 conidia/ha as a foliar spray in the evening (UV sensitivity requires evening application) at 500–1000 L water/ha, or as a soil drench against soil-dwelling pests. Maintain humidity above 70 % for 24–48 hours after application — germination requires high humidity. Apply during the target pest's most vulnerable life stage (typically early instars).
🌿 Organic treatments
- Foliar spray with M. anisopliae wettable powder @ 5 g/L (1×10^8 cfu/g) in the evening; soil drench @ 5 kg/ha against soil-dwelling pests; oil-based ULV formulation @ 1 L/ha for palm injection against rhinoceros beetle; granular formulation @ 10 kg/ha against white grubs in sugarcane; tank-mix with 0.05 % glycerol or 0.1 % skim milk as UV protectant; repeated applications every 14–21 days during the pest's active season.
🧪 Chemical treatments
- No chemical treatment needed — beneficial agent. Compatible with most biological insecticides (Bt, NPV, azadirachtin, neem oil) but incompatible with most chemical fungicides (carbendazim, mancozeb, copper oxychloride) — apply separately with at least 7 days gap. Avoid tank-mixing with benomyl, thiophanate-methyl, or trifloxystrobin — all toxic to M. anisopliae.
🛡️ Prevention
- No prevention needed — this is a beneficial biocontrol fungus. To conserve naturally occurring populations: maintain soil organic matter above 1.5 % (apply FYM, compost, or green manure); maintain diverse crop canopies that conserve humidity; avoid broad-spectrum fungicides (carbendazim, mancozeb, copper oxychloride) that kill entomopathogenic fungi; use minimum-till or no-till practices to preserve fungal inoculum in the top 10 cm of soil; rotate with cover crops (sunhemp, horse gram) that support alternative insect hosts and sustain fungal populations between crops.
🪴 Affected plants
- Polyphagous entomopathogenic fungus with an extremely broad host range (>200 insect species across 7 orders). Used in India against rhinoceros beetle (Oryctes rhinoceros) in coconut, white grubs (Holotrichia spp.) in sugarcane and groundnut, rice stem borer (Scirpophaga incertulas), coffee berry borer (Hypothenemus hampei), grasshoppers, termites, and mosquito larvae in public health.
🦋 Natural predators
- As a biocontrol fungus, M. anisopliae has few significant natural enemies. Soil-dwelling mites (Mesostigmata) and springtails (Collembola) may feed on surface mycelium; certain soil bacteria (Pseudomonas spp., Bacillus spp.) produce antifungal compounds; the fungus itself is parasitised by mycoparasitic fungi (Trichoderma spp., Gliocladium spp.) in soil.
🌱 Host plants
- Polyphagous biocontrol agent — does not feed on plants. Used against coconut rhinoceros beetle, sugarcane and groundnut white grubs, rice stem borer, coffee berry borer, grasshoppers, termites, and mosquito larvae.
🔄 Lifecycle
- Conidia attach to insect cuticle and germinate in 12–24 hours under high humidity; penetration pegs invade cuticle and reach haemocoel in 24–48 hours; blastospores proliferate in haemocoel and produce destruxin toxins that kill host within 5–10 days; mycelium emerges from cadaver and sporulates under humid conditions in 24–48 hours; conidia disperse to new hosts.
- Total lifecycle 7–14 days inside host at 28°C; conidia survive 6–12 months on leaf or soil surfaces under cool dry conditions.
📅 Season
- Active year-round in moist tropical Indian conditions; application efficacy peaks during the warm humid months (June–November) when humidity is favourable for conidial germination and target pest larvae are active.
🔎 Appearance
- Visible growth appears as a characteristic olive-green to dark green velvety mould on the surface of infected insect cadavers — the diagnostic colour that gives the disease its common name 'green muscardine'.
- Under the microscope, conidiophores bear chains of oval, single-celled conidia 5–10 μm long.
- The fungus penetrates the insect cuticle directly using specialised penetration pegs and appressoria, then proliferates inside the haemocoel as yeast-like hyphal bodies (blastospores) 3–8 μm long.
💥 Damage level
- Beneficial
🔁 Reproduction rate
- Moderate
🗺️ Geographic regions
- Indian Subcontinent (pan-India
- native to Indian soils)
- pantropical and warm-temperate through biocontrol deployment; cosmopolitan in tropical
- subtropical
- and warm-temperate soils worldwide.
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