MushroomFarming / article

Oyster spawn run

Observe colonization progress, contamination pattern and substrate condition before changing to fruiting. Evidence, method and India-context boundaries remain visible.

Practical explanation + detailed referenceSources & review ↓

Real cultivation photograph. Read its source for location and context; it is not a universal operating specification.Livehealthy · CC BY-SA 4.0View full photograph ↗

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Understand the topic

What you need to know.

Spawn run is the stretch after spawning when oyster mycelium grows from the spawn grains through the whole bag. This page covers the conditions ICAR-DMR sets for it, what healthy colonisation looks like, the signs of contamination and what to do about them, and how to tell that the run is over. Mixing spawn and filling bags are on the spawning page.

Teaching revised 2026-09-24. Source-linked editorial synthesis; this date does not imply independent technical review.

Part 01

What the mycelium does inside a closed bag

Once a bag is spawned, every grain of spawn is a starting point. White threads of mycelium grow out from each one into the straw and join up with threads from the grains around them, until the whole mass is bound together. The mycelium of most Pleurotus species is pure white, so a healthy bag turns steadily whiter.

The oyster folder expects the mycelium to spread over all the straw in about 15 to 25 days, when the bags look white. The manual describes the end point as a thick mycelial mat right through the substrate; only then is the bag ready for fruiting. It also sets a floor: bags should in no case be opened before 16 to 18 days. Two species are the exception. P. membranaceus and P. djamor var. roseus can form mushrooms within 10 days, through the small holes of a closed bag.

The room's job during these weeks is to hold the right temperature and otherwise leave the bags alone.

Sources: ICAR-DMR manual, 2011 · ICAR-DMR oyster folder

Chopped yellow straw partly covered and bound by dense white mycelium. — White mycelium of golden oyster (Pleurotus citrinopileatus) binding chopped straw together during spawn run. Photo: Rob Hille, CC BY-SA 3.0. Source

Part 02

The conditions ICAR-DMR sets for the run

The manual gives one temperature range for oyster mycelium, and its round-the-year table gives separate spawn run bands by species. Where the manual states two different figures, both are shown. Measure inside the bags as well as in the room.

Mycelial growth range10 to 30 °COptimum 22 to 26 °C. Elsewhere the same chapter says growth of all Pleurotus species takes place at 20 to 30 °C.

Upper limitabove 30 °CHigher temperature inhibits growth and kills the mycelium.

Bags above room air2 to 4 °CBed temperature is generally this much higher than the room.

Species band, P. florida25 to 30 °C25 to 32 °C for P. sajor-caju; 18 to 22 °C for P. eryngii.

Carbon dioxide the mycelium tolerates15 to 20 %The incubation section's figure. Another section of the same manual gives up to 2 percent (20,000 ppm) during spawn run.

pH during colonisation6.0 to 7.0

Source: ICAR-DMR manual, 2011

Part 03

No water, no air, no light: keep the room closed and cool

The oyster folder is plain about this stage: while the spawn spreads, the bags need no water, no air and no light. The manual agrees. Bags are not opened and no ventilation is given, and because high humidity is not needed, no water is sprayed. The mycelium copes with carbon dioxide levels that would spoil a fruiting crop, so a shut room does it no harm.

Bags can stand on a raised platform or shelves, or hang in the cropping room. What needs watching is heat. The manual asks for the daily maximum and minimum temperature of the room and of the beds to be written down. If the bags or the room start climbing above 30 °C, the folder says to sprinkle water on the walls and roof two to three times, or to run an air cooler, and to make sure no water collects on the bags.

Look at every bag at least once a week to confirm the spawn is spreading.

Sources: ICAR-DMR oyster folder · ICAR-DMR manual, 2011

Wooden shelves stacked with rows of capped substrate bags, many of them white with mycelium. — Shelves of substrate bags turning white as mycelium grows through them, at a farm in the Cameron Highlands, Malaysia. Photo: Arne Müseler, CC BY-SA 3.0 DE. Source

Part 04

Warning signs to look for on each weekly round

The manual lists a long run of competitor fungi found in oyster substrate, among them Trichoderma, Aspergillus, Penicillium, Mucor, Rhizopus and Coprinus. You do not need to name one to act on it. Colour, bare patches, heat and flies are the things to check.

Green, black or blue mould on the straw or through the bag wall. The oyster folder treats any of these as a reason to remove the bag.
Patches that stay bare or thin while the rest of the batch has turned white.
Bags or room running above 30 °C, a temperature that kills oyster mycelium.
Mould turning up in a batch that was left too long or ran too hot; the manual links competitor moulds to both.
Flies around the bags. The manual notes that mushroom flies get through ordinary wire screen and breed in spawned material and mushroom beds.

Sources: ICAR-DMR manual, 2011 · ICAR-DMR oyster folder

Close view of two plastic substrate bags; one is streaked dark green and grey, the other is brown with pale growth. — Two substrate bags from a farm in the Cameron Highlands, Malaysia. The left bag is covered in dark green mould instead of white mycelium. Photo: Arne Müseler, CC BY-SA 3.0 DE. Source

Part 05

Open, wait or remove: deciding bag by bag

Work through the batch from clean bags to suspect ones, and wash your hands between them.

IfA bag shows green, black or blue mould: ThenTake it out of the growing room without opening it and dispose of it well away from the farm, as the oyster folder directs.
IfGrowth is patchy but there is no mould: ThenLeave the bag a few more days to finish. The manual does this rather than discarding it.
IfThe bag is white right through and has had at least 16 to 18 days: ThenIt is ready for fruiting. Opening the bag and changing the room are covered on the fruiting page.
IfBag temperature passes 30 °C: ThenCool the room the same day with water on walls and roof or an air cooler, keeping the bags themselves dry.
IfPinheads appear through the holes within 10 days: ThenThe manual expects this in P. membranaceus and P. djamor var. roseus. In other species, check your temperature records before changing anything.

Sources: ICAR-DMR oyster folder · ICAR-DMR manual, 2011

Part 06

Mistakes that spoil a run that started well

Common mistakeOpening bags early because the surface looks white.

Do this insteadWait for a thick mat right through and at least 16 to 18 days. The manual makes exceptions for two species only.

Common mistakeSpraying the bags to keep them fresh.

Do this insteadThe manual gives no water and no high humidity during the run, and the folder warns against water collecting on the bags.

Common mistakeReading the thermometer by the door.

Do this insteadMeasure among the bags too. Beds run about 2 to 4 °C warmer than room air.

Common mistakeLeaving doors and ventilators unscreened.

Do this insteadScreen them with nylon net of 35 mesh or finer, which the manual says checks the entry of flies.

Common mistakeKeeping a failing batch in the room in the hope it recovers.

Do this insteadRemove mouldy bags promptly. The manual links mould outbreaks to crops kept too long and to high temperatures.

Sources: ICAR-DMR manual, 2011 · ICAR-DMR oyster folder

Go deeper

Technical reference, records and tools.

Detailed crop-stage information, parameters, diagrams and specialist tools are kept together below. This material retains its source conditions and review limits.

Open the complete technical reference

oyster · cultivation stage

Oyster spawn run

Observe colonization progress, contamination pattern and substrate condition before changing to fruiting. Evidence, method and India-context boundaries remain visible.

Publication: Editorial review in progress
Evidence records: 5
External review: Not yet recorded
Wild ID: Not provided

The oyster bag method in six steps

Source: ICAR-DMR oyster folder and the 2011 manual.

Chop the strawWheat or paddy straw cut to 2 to 3 cm (manual method uses 5 to 10 cm).Day 0
Hot-water treatmentFolder: 60 to 65 °C for 20 to 30 minutes (manual: 65 to 70 °C for one hour), then drain off the excess water.Day 0
Spawn and fill bags2 to 3 percent spawn on wet-straw weight, in layers; 10 to 12 holes per bag (manual: 10 to 15).Day 0
Spawn run22 to 26 °C in the dark for 15 to 25 days until the bag is white through.Days 1 to 25
Open the bag and fruitLight, fresh air, 75 to 85 percent humidity, CO₂ below 600 ppm (folder: 800 ppm). Pins in about a week.From day 16
Harvest and next flushNext flush 8 to 10 days later. Manual: 500 to 700 kg from one tonne of dry straw in 45 to 60 days.Up to day 60

Quick orientation

Observe colonization progress, contamination pattern and substrate condition before changing to fruiting. This topic belongs to a Pleurotus substrate-bag or validated block system. The species or strain, substrate treatment and fruiting-air context must travel together.

Why this stage matters

Observe colonization progress, contamination pattern and substrate condition before changing to fruiting.

Method boundary

This topic belongs to a Pleurotus substrate-bag or validated block system. The species or strain, substrate treatment and fruiting-air context must travel together.

Confirm the culture as Pleurotus spp., with strain or variety recorded where available.
Confirm one method: straw bag or validated lignocellulosic bag or block.
Record substrate source, treatment class, batch and contamination observations.

Observe and record

Use batch records, stage dates, room observations and contamination patterns. Compare the crop with its own prior condition before changing several variables at once.

Evidence status

The page publishes process relationships supported by primary institutional sources. Numeric recipes remain absent where source context, strain identity or specialist review is incomplete.

Production method records

One species can require more than one cultivation model.

OYS-STRAW-BAG

Treated straw bag system

Substrate: clean cereal straw with method evidence
Container: perforated or opened cultivation bag
Treatment: Pasteurization-class treatment or another validated method; not interchangeable with sterilization.
Scale context: home trial to commercial batch, with different hygiene and climate responsibilities

Material check
Treatment
Cooling and moisture check
Spawning
Spawn run
Fruiting transition
Cluster harvest

Trace the boundary

Evidence and limitations

institutional · tier AResearch programmes

Current institutional scope for cultivated and specialty mushroom research in India.

Research scope does not by itself establish a farm recommendation, commercial readiness or strain-specific operating range.

Open primary source

technical-bulletin · tier ATechnologies developed by ICAR-DMR

Institutional method history for oyster, milky, paddy straw, shiitake and selected specialty mushrooms.

Method descriptions are context-specific and contain numeric and broad substrate statements that require independent technical review before operational publication.

Open primary source

current-advisory · tier ACurrent crop advisory

Time-stamped Indian seasonal crop context and the need to choose oyster species for conditions.

Chemical directions are excluded from this platform unless a current label and jurisdiction are independently verified.

Open primary source

technical-bulletin · tier AOyster mushroom cultivation FAQ

Indian institutional distinction between warm- and cool-fruiting Pleurotus species, plus an occupational spore-exposure warning.

The species bands are source context, not a strain guarantee. Generic yield, storage and legacy chemical statements are not carried into operational guidance.

Open primary source

technical-bulletin · tier APost-harvest technology of mushrooms

Species-specific post-harvest deterioration patterns and handling context.

Historic shelf-life statements depend on maturity, handling, packaging and storage conditions and are not reproduced as guarantees.

Open primary source

Read the evidence

Sources & review.

Editorial update: 2026-09-03. Independent technical review is not recorded for this entry.

Research programmes ↗
ICAR Directorate of Mushroom Research
Technologies developed by ICAR-DMR ↗
ICAR Directorate of Mushroom Research · 2020
Current crop advisory ↗
ICAR Directorate of Mushroom Research · 2026
Oyster mushroom cultivation FAQ ↗
ICAR Directorate of Mushroom Research
Post-harvest technology of mushrooms ↗
ICAR Directorate of Mushroom Research

Reading a source is not the same as applying its instructions to every farm. Confirm species, strain, crop stage, system, region and publication date. Old chemical recommendations are not current-use instructions.

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