Most commercial mushroom farms do not lose yield to one big catastrophe. They lose it to a slow, unnoticed drift — a Trichoderma infection that spreads across three rooms over a fortnight, a cobweb patch that gets written off as “normal”, a sciarid fly population that doubles every cycle. By the time a farm realises it has a disease problem, it has usually already had the problem for weeks. This guide covers the diseases and pests that most commonly affect Agaricus bisporus in Indian growing conditions, with practical control measures for each.
Fungal diseases
Green mould (Trichoderma aggressivum)
The most feared contamination in commercial mushroom production. Appears as bright green patches on the compost surface, spreading rapidly and killing mycelium in its path. Root causes are almost always traced back to inadequate Phase II pasteurisation, contaminated spawn, or cross-contamination from tools and clothing. Control is prevention: strict sanitation of tunnels, dedicated room tools, foot dips at every doorway, and never letting visitors or non-essential staff enter active rooms.
Cobweb disease (Cladobotryum dendroides)
A soft, white, fast-growing mycelium that spreads over casing and covers mushrooms like a spider web. Thrives in high humidity and poor air movement. Affected patches should be covered with salt or a dilute iodophor solution before removal to prevent sporulation. Improve airflow, reduce casing surface wetness, and tighten casing sanitation.
Dry bubble (Lecanicillium fungicola)
Causes deformed mushrooms with brown, dry, tumour-like swellings. Spread by casing soil, flies, and water droplets. Use steam-pasteurised casing, keep casing moisture on the lower side, and rigorously control fly populations between cycles.
Wet bubble (Mycogone perniciosa)
Produces white, wet, gooey deformities often with an unpleasant odour. Almost always a casing soil contamination. The fix is upstream: test casing batches, avoid using casing from suspect sources, and steam-treat casing where practical.
Bacterial diseases
Bacterial blotch (Pseudomonas tolaasii)
Yellow-brown sunken spots on mushroom caps. Worst in rooms with water sitting on caps for extended periods. Reduce watering volumes, water earlier in the day so caps dry before dark, improve air circulation, and ensure water quality is not the source — a water chlorination check is often revealing.
Mummy disease
Mushrooms emerge deformed, leathery, and fail to mature. Often linked to a bacterial complex spreading through the compost. Affected rooms should be fully cooked-out (steam-sterilised) between cycles and the compost source should be reviewed.
Insect pests
Sciarid flies (Lycoriella)
The most common fly pest at Indian farms. Larvae feed on mycelium and pins, adults spread fungal and bacterial spores between rooms. Control combines physical exclusion (insect screens on intakes, positive pressure rooms), sanitation between cycles, and targeted use of approved IGRs like diflubenzuron. Sticky traps at doorways are a surprisingly useful monitoring tool.
Phorid flies (Megaselia)
Smaller and faster than sciarids, phorids are attracted to decaying organic matter and are particularly common in farms with poor spent-compost management. Same control principles — screens, sanitation, pressure — plus rigorous removal of spent compost and waste from the farm boundary.
Mites
Hitchhike in on straw and compost. Most species are harmless or even beneficial, but some feed directly on mycelium or mushrooms. Proper Phase II kills the vast majority; mite problems typically indicate a composting temperature that was too low.
Biosecurity: the real control strategy
Reactive disease management is a losing game in mushroom farming. Once contamination is visible on a crop, most of the damage is already done and the cost of losing that flush far exceeds any treatment. The farms that stay clean run disciplined biosecurity: foot dips, hand sanitation, dedicated tools per room, positive air pressure, strict visitor policies, and — critically — a full cook-out between cycles using live steam to sterilise spent compost before removal.
Record, photograph, and trace
Every quality defect worth worrying about is worth photographing. Modern farm management software allows workers to attach photos to quality inspections, building up a visual record your team and buyers can reference. The farms that improve year-on-year are the ones that treat every defect as a traceable event — logged with the room number, the compost lot, the casing batch, and the exact date — rather than a random cost of doing business.
The bottom line
Mushroom disease and pest management is 80% prevention and 20% response. Invest in the prevention, and the response becomes the rare exception rather than the weekly routine.