Cultivation of Oyster Mushrooms
College of Agricultural Sciences
Agricultural Research and Cooperative Extension
Total mushroom production worldwide has increased more than 18-fold in the last 32 years, from about 350,000 metric tons in 1965 to about 6,160,800 metric tons in 1997. The bulk of this increase has occurred during the last 15 years. A considerable shift has occurred in the composite of genera that constitute the mushroom supply.
Oyster mushrooms are grown from mycelium
(threadlike filaments that become interwoven) propagated on a base of steam-sterilized cereal grain
(usually rye or millet). This cereal grain/mycelium mixture is called spawn and is used to seed mushroom substrate. Most spawn is made with mycelium from a stored culture, rather than mycelium whose parent was a spore.
Before 1970, cultivars used for commercial spawn production were maintained on various agars or cereal grains with periodic subculturing of growing mycelium to a fresh medium. This method, for the most part, was reliable, although spawn makers and researchers reported cases of culture degeneration periodically.
Substrate preparation. In the United States, the primary ingredients used for Pleurotus spp. production are chopped wheat straw
(Triticum aestivum L) or cottonseed hulls
(Gossypium hirsutum L) or mixtures of both. For production on wheat straw, the material is milled to a length of about 2 to 6 cm.
In Japan, bottle production of oyster mushrooms is most common. Bottle production also is increasing in popularity in the United States. Substrate is filled into bottles contained in trays
(usually 16 bottles per tray), sterilized, and inoculated with Pleurotus spp. spawn.
After spawning, the bags or bottles may be moved to a spawn run room where air temperature is maintained at 18–20°C. Relative humidity is maintained at 95 to 98 percent to minimize drying of the substrate surfaces. Only recirculated air is used for cooling and air distribution. The first 12 to 21 days of spawn run may be completed without artificial lighting.
Marketing of oyster mushrooms in the United States is a relatively new enterprise. Since 1984, some farms have seen their production rise as prices have fallen. In the 1996–1997 growing season, growers received about $5.70/kg
($2.59/lb) for oyster mushrooms. From 1997 to 2002, the price of oyster mushrooms has declined an average of $0.22/kg
($0.10/lb) per year to $4.40/kg
($2.00/ lb).
Bacteria. The most common bacterial problem encountered by growers is Pseudomonas tolaasii. This is the same bacterium that causes bacterial blotch of A. bisporus. Symptoms of the disease include reduced yield and orange discoloration and brittleness of the basidiocarps. Infected mushrooms have a reduced shelf life.
As consumers become more aware of the additional culinary characteristics offered by a variety of mushrooms, demand for oyster mushrooms will increase. The development of improved technology to cultivate each species more efficiently will allow the consumer price to decline. At the same time, product quality should increase, thus furthering demand.