Fungiculture

Fungiculture is the cultivation of mushrooms and other fungi. Cultivating fungi can yield food, medicine, construction materials and other products. A mushroom farm is in the business of growing fungi.

The word is also commonly used to refer to the practice of cultivating fungi by leafcutter ants, termites, ambrosia beetles, and marsh periwinkles.

Introduction

Mushrooms are not plants, and require different conditions for optimal growth. Plants develop through photosynthesis, a process that converts atmospheric carbon dioxide into carbohydrates, especially cellulose. While sunlight provides an energy source for plants, mushrooms derive all of their energy and growth materials from their growth medium, through biochemical decomposition processes. This does not mean that light is an irrelevant requirement, since some fungi use light as a signal for fruiting. However, all the materials for growth must already be present in the growth medium. Mushrooms grow well at relative humidity levels of around 95–100%, and substrate moisture levels of 50 to 75%.[1]

Instead of seeds, mushrooms reproduce through spores. Spores can be contaminated with airborne microorganisms, which will interfere with mushroom growth and prevent a healthy crop.

Mycelium, or actively growing mushroom culture, is placed on a substrate—usually sterilized grains such as rye or millet—and induced to grow into those grains. This is called inoculation. Inoculated grains (or plugs) are referred to as spawn. Spores are another inoculation option, but are less developed than established mycelium. Since they are also contaminated easily, they are only manipulated in laboratory conditions with a laminar flow cabinet.

Techniques

All mushroom growing techniques require the correct combination of humidity, temperature, substrate (growth medium) and inoculum (spawn or starter culture). Wild harvests, outdoor log inoculation and indoor trays all provide these elements.

Outdoor logs

Mushrooms can be grown on logs placed outdoors in stacks or piles, as has been done for hundreds of years.Sterilization is not performed in this method. Since production may be unpredictable and seasonal, less than 5% of commercially sold mushrooms are produced this way.[4] Here, tree logs are inoculated with spawn, then allowed to grow as they would in wild conditions. Fruiting, or pinning, is triggered by seasonal changes, or by briefly soaking the logs in cool water. Shiitake and oyster mushrooms have traditionally been produced using the outdoor log technique, although controlled techniques such as indoor tray growing or artificial logs made of compressed substrate have been substituted.

Shiitake mushrooms grown under a forested canopy are considered non-timber forest products. In the North-Eastern US, shiitake mushrooms can be cultivated on a variety of hardwood logs including oak, American beech, sugar maple and hophornbeam. Softwood should not be used to cultivate shiitake mushrooms as the resin of softwoods will oftentimes inhibit the growth of the shiitake mushroom making it impractical as a growing substrate.

In order to produce shiitake mushrooms, 1 metre (3-foot) hardwood logs with a diameter ranging between 10–15 cm (4–6 in) are inoculated with the mycelium of the shiitake fungus. Inoculation is completed by drilling holes in hardwood logs, filling the holes with cultured shiitake mycelium or inoculum, and then sealing the filled holes with hot wax. After inoculation, the logs are placed under the closed canopy of a coniferous stand and are left to incubate for 12 to 15 months. Once incubation is complete, the logs are soaked in water for 24 hours. 7 to 10 days after soaking, shiitake mushrooms will begin to fruit and can be harvested once fully ripe.

Indoor trays

Indoor growing provides the ability to tightly regulate light, temperature and humidity while excluding contaminants and pests. This allows consistent production, regulated by spawning cycles.[10] This is typically accomplished in windowless, purpose-built buildings, for large-scale commercial production.

Indoor tray growing is the most common commercial technique, followed by containerized growing. The tray technique provides the advantages of scalability and easier harvesting. Unlike wild harvests, indoor techniques provide tight control over growing substrate composition and growing conditions; this makes harvests much more predictable.

According to Daniel Royse and Robert Beelman, "[Indoor] Mushroom farming consists of six steps, and although the divisions are somewhat arbitrary, these steps identify what is needed to form a production system. The six steps are composting, fertilizing, spawning, casing, pinning, and cropping."