Optimal Growth Conditions for Oyster Mushroom, especially during Fruiting

Writer: Duk-hwan Kim / Date :2001-04-01 / hits: 148

Recent days have seen diversification of oyster mushroom varieties with strong mycelial growth. Yet, some mushroom farmers might lose their crop, facing some unwelcome cases: with temperature getting higher since mid-April, colonization of mycelia often occurs while mushroom fully grows up, or fruitbody development turns out to be poorer or fruiting itself doesn't occur at all, as outside air gets too dry. Growers need to take care to provide optimal growth conditions for mushroom, especially during fruiting.
Mushroom Growth Parameters
* Lighting
Light has a close relationship with mushroom's color and plays an important role in fruitbody development.
Poor or no light will lead to a crop failure or at least a reduced mushroom production. Oyster mushroom requires indirect lighting.
If lighting is insufficient, color of mushroom would be white and stalk enlongated. Therefore make sure of maintaining 120 lux light during a day.
* Temperature
Oyster mushroom continues a vegetative growth stage at 20-25'C, but shifts itself to a reproductive growth stage below 15'C.
It is desirable for mushroom growers to lower temperature to a lowest limit of optimal temperature, since temperature for mushroom development varies among mushroom varieties. In order to prevent the substrate block from losing moisture and being contaminated with various germs, growers should let the light in and lower the room temperature with plastic covering on the block.
* Ventilation
Right after removing plastic cover, open ventilation windows for 30-40 minutes for air-exchanges. After that, leave just a few ventilation windows open 4-5 cm wide.
Oyster mushroom shows a stunted growth by carbon dioxide if ventilation was poorly done during pinning and fruitbody development. The mushroom also attracts various contaminants including green mold to a spot where mycelial colonization is not enough.
Excessive ventilation can cause heavy water loss and hardening of the substrate, with fruitbodies turning brown.
It is advisable to ventilate consecutively on a regular basis.
Growers are well recommended to use poly-ethylene duct when blowing fresh air into the growing room.
* Humidity and Moisture Content
After ventilation, raise the room humidity by spraying underground water onto corridors and into the air.
In order to prevent abrasion of the substrate surface and suffocation of young mushrooms, indoor humidity should be maintained above 90%. The mushroom doesn't require frequent watering at an early stage of fruit-body development.
Mushroom development and harvesting control
Lower indoor humidity when pinheads appear on the substrate and initiate reproductive growth. Increase watering frequency depending on the fruiting rate.
After sprinkling, ventilate the growing room sufficiently until all water droplets on the surface of mushroom are gone.
If a mushroom absorbs too much free water, its texture gets too soggy.
Free water on the substrate makes mushrooms susceptible to bacterial blotch.
In winter or for young mushrooms, reducing watering time and ventilation frequency goes a long way toward heading off disease outbreaks.
The main causes for young mushroom's wilting and shriveling during harvesting period include excessive watering, high temperature and poor ventilation. Growers can find out whether watering is sufficient or not by holding young mushrooms slightly. When you give young mushrooms too much water, they will ooze water, when pinched.
At high temperatures, mushrooms which seem to wilt from the upper end of the substrate block don't ooze water.
If ventilation is poor provided, the stipe gets enlongated and cap remains small. Often young mushrooms begin to wilt from the middle or upper part of the block.
In 3~4 days of fruiting, indoor humidity should be lowered to 85~95%. During harvesting period 80~85% of indoor humidity could guarantee satisfactory mushroom quality.
90% of indoor humidity as in an early stage could cause malformed mushrooms or abnormal mycelial growth on the mushroom cap.
Excessive moisture could cause the lack of oxygen in the substrate, which, in turn, keeps mycelia from a vigorous growth and condemns mushroom to a delayed and stunted growth along with distant gills and a thin cap.
When both substrate and room humidity are low, mushroom growth will be stunted due to lack of water. Even in a stage of young mushroom, cap upturns earlier and releases more spores.
Ventilate the growing room every 3 hours for a complete air exchange between indoor and outdoor air.
At low temperatures, growers are highly likely to ventilate less frequently to maintain indoor temperature. Thus, they are recommended to water during mid-day and ventilate enough but to avoid ventilation during mid night for indoor temperature to be kept in line.
When the room temperature goes up higher than the optimal temperature during fruitbody development, mushrooms should get enlongated stipes.
Humidity and ventilation management in the growing room is one of the most important factors determining the length of stipe and resistance to contaminants.
After harvesting, immediately get rid of mushroom remains scattered on the substrate blocks.
The second flush (a synchronized fruiting of mushrooms) is induced as with primordia induction by watering inside the growing room and on the shelf racks block and maintaining temperature and providing lighting, after applying pesticides to mushroom blocks.
Abnormal Symptoms and Remedies during Fruiting
* Mycelia dying from heavy water loss
Although waste cotton block holds enough water inside, its surface is likely to dry out. Yet, cultivation on rice straw shows less damages from moisture loss, since rice straw in the bottom part of the block holds water through straw's capillary action.
If the surface of the block gets dry, the mushroom block attracts green molds easilier , with spawn run and colonization delayed. -->Remedies includes preventing excessive drying after inoculation, and maintaining air humidity high up to 90~95% after cold shock.
-->In the case of cultivation on waste cotton, use humidifiers.
-->Make sure to maintain the optimum humidity level by sprinkling water on the floor.
* Fruiting failure due to a mycelium lump developing on the substrate surface
Mycelia seem to grow normal even on the surface of waste cotton substrate. During fruitbody development, however, fully grown-up mycelium is prone to lumping and looks like a fried egg. From the center of the spot, where lumps of mycelia appear on the surface, mycelia start to turn brown, with fruiting delayed and mushroom quality degraded. Sometimes mushroom decay to ooze brownish fluid.
Although causes for those symptoms vary among mushroom varieties, they occur when gas is over concentrated, waste cotton is over-moistened or mycelia grow too fast due to high temperatures in the block.
When the surface of the block dries too fast and mycelia make a thick lump on the substrate surface or gets dry.
--> Remedy : frequent ventilation along with heating will do the trick.
--> Those symptoms can occur if indoor temperature is maintained low even when temperature inside the block is high. Make sure adequate temperatures of the growing room and the substrate should be maintained. Growers might want to scratch off the mycelium lump or to remove some of them from the block.
* Much smaller mushrooms and those wilting to death
Although young mushroom develop in large numbers, they can not be fully grown up, remaining young and small with earlier cap upturning. Those mushrooms will be eventually dried out.
When you knock the dried mushroom block, you can hear sounds like drum to indicate there is an empty room inside the block. That is because the inner part of the substrate block can easily degrade due to proper temperature and moisture inside the block, with its size slightly reducing. But the surface of the block forms a thick skin as mycelia get entangled on the dry surface.
Mushrooms developed under these circumstances fail to connect with mycelia inside the block, which hinders water and nutrition supply necessary for mushroom growth.
---> Remedy: irrigate the block with enough water after cutting the surface of the block at a certain distance. The substrate colonized with oyster mushroom mycelia absorbs the irrigated water, which links the floating layers together, removing empty space inside the block. This process helps mushrooms to grow.
---> Make sure to drain extra water by making tiny holes in plastic cover on the floor, lest it should remain on the covering.