Growing mushrooms at home is a rewarding activity. But it is not without its challenges. Contamination is one of the biggest problems that mushroom cultivators encounter.
Mushrooms and mold thrive in the same environment. This article will discuss some common mistakes that cause contamination and offer tips to avoid them.
1. Overwatering
When growing mushrooms, you’ll need to provide the substrate with a certain level of dampness to ensure proper growth. However, this is not a case of more is better; overwatering can be quite dangerous for your crop. Excess moisture leads to the breakdown of mycelium, a process that inhibits mushroom development. This can lead to dry, unappetizing specimens. It can also encourage the growth of unwanted fungi that may harm your crop.
A good way to prevent overwatering is to monitor the humidity of your grow space with a hygrometer. You should aim for a humidity level around 80-90% during the fruiting phase of your crop. You’ll want to keep an eye on this number, as it will fluctuate based on the climate and weather conditions in your area.
To achieve high humidity levels, it is important to properly pasteurize and sterilize your substrate materials. This will help to eliminate contaminants that could hinder the growth of the mycelium and spoil your yields. It is also important to maintain a consistent air exchange rate in your growing room, especially once your mushrooms are ready to fruit. This helps to reduce the build-up of carbon dioxide, which can be fatal for mushrooms.
2. Poor Substrate
When mushroom growers work with straw or other natural materials to cultivate their crop, they must properly pasteurize and sterilize the substrate before adding their spores. Inadequate preparation can lead to contamination that robs mushrooms of the nutrition they need to thrive. It is also important to select a substrate that matches the specific species of mushroom you’re growing. Straw and similar agricultural products are ideal for growing oyster mushrooms, while reishi and lion’s mane require wood-based substrates.
Substrates are also susceptible to contaminants that may not be visible to the naked eye. For example, contaminated straw can harbor bacteria that outcompetes mycelium for nutrients. Inadequate preparation of the substrate can also introduce unwanted molds. These undesirable organisms can be killed by soaking the substrate in a solution of hydrogen peroxide and water for a day.
Using the wrong type of substrate for a particular mushroom also hinders growth. Some types of mushrooms require a casing layer, which is a non-nutritious top layer applied to fully colonized bulk substrate for moisture retention and pinning.
Another common mistake is to inoculate the substrate too soon after sterilization. This slows down colonization and increases the risk of contamination. It is essential to use clean hands and tools and work in front of a laminar flow hood when handling the spores. Those who are serious about their growing should invest in specialist equipment such as a pressure cooker and laminar flow hood to reduce airborne contaminants that can enter the growing environment. It is also important to avoid contaminating the substrate with other spores such as grain spores, which can compete for nutrients with mycelium. If contamination is detected, the contaminated straw or grain should be destroyed immediately, and not using monotub kits.
3. Pests
Many mushroom growers are unaware of the existence of a number of pests that can negatively impact their production. They can cause contamination or destroy the entire crop. They can also transmit diseases, such as white plaster mold caused by the Scopulariopsis fimicola fungus or bacteria spot (caused by Pseudomonas tolaasii bacterium). The presence of these pests can be reduced by properly sterilizing compost and casing materials, using sterile bags and by selecting resistant mushroom varieties.
Mushroom flies (Calliphoridae, Culicidae, Drosophilidae) and mites (Mycophagous and Saprophagous Mites) are the main pests of mushrooms. They damage the mushroom caps, suffocate the mycelium and cause shrunken and deformed heads. In addition, the larvae of some dipterous flies can perforate the stipe and stipe-pileus in Pleurotus species causing a significant decline in the yield2.
Another issue is the spread of nematodes by insects or mechanical means. Nematodes can be extremely damaging and result in poor production or even complete loss of a crop. They can also be spread from one culture to another by contaminated equipment and debris. They are particularly problematic for growers using a straw substrate.
In addition, the use of improper irrigation and growing materials can lead to an accumulation of excess moisture that creates a breeding ground for molds and other pests. It is important to follow the watering schedules of each mushroom variety and ensure that the soil has sufficient drainage between watering. Inspect the grow area regularly to check for signs of infestation or disease. Use a natural insecticide, such as Safer Brand BioNEEM Insecticide with Neem Oil Concentrate to keep insects away. This ready-to-use spray kills hard bodied and soft bodied insects on contact. It is available in a gallon size, which treats up to 700 square feet.
4. Temperature Changes
Mushrooms require a specific temperature range in order to thrive. If temperatures are too low, the mycelium will slow down or even stop growing, resulting in stunted growth and lower yields. Likewise, if temperatures are too high, the mycelium may burn up, leading to poor fruiting and potentially diseased mushrooms.
For these reasons, it is important to make sure that your grow space has a steady environment with an ideal range of temperatures. This can be done with a variety of tools, including thermometers/temperature sensors, heating pads or mats, cooling fans, and greenhouses. Depending on the species of mushroom you are trying to grow, each of these methods will provide different levels of control and may be best for your particular needs.
Aside from temperature, humidity is also key for successful mushroom growth. A good amount of dampness is necessary for the mushrooms to be able to absorb moisture through their cell walls, which in turn helps them mature and produce spores. Too little humidity, however, can lead to dry mushrooms and a decreased yield. A hygrometer can be used to monitor humidity levels, and a spore mister can be added to the mix to help maintain a suitable level.
Finally, it is important to note that any time you are working with your mushroom crop, the work area should be kept clean and sterile. This is especially true when inoculating the substrate with spores or other chemicals. This can be accomplished by following a strict contamination prevention protocol, such as sterilizing any equipment before and after using it and always using a fresh batch of sterile glycerin for each inoculation or manipulation. Additionally, any contaminated materials should be immediately removed from the work area and destroyed in a safe and sanitary manner.
5. Thermogenesis
When it comes to growing mushrooms, the right environment is key. This includes the temperature, humidity, and ventilation. But there is a danger that many home growers overlook: the potential for the mushroom substrate to produce too much heat through a process called thermogenesis. Thermogenesis is the physiological activity of internally releasing heat energy, and it is found in all living organisms. It plays a variety of roles in the body, from maintaining core temperature during cold exposure to shivering thermogenesis, which occurs when skeletal muscles work against gravity to generate heat energy.
Mushrooms require a high level of humidity, typically 85-95% relative humidity. This is important to prevent the mushrooms from drying out or becoming damaged by low levels of oxygen (O2). If humidity is too low, it can result in poor fruiting or mycelium death. Conversely, if humidity is too high, it can lead to the formation of molds and other harmful substances that could negatively impact the mushrooms.
Thermogenesis is also an important part of the metabolic process, converting food into energy that the body can use for various functions. Obligatory thermogenesis is the production of heat for essential body functions such as circulation, breathing, and digestion. Postprandial thermogenesis is the production of heat after a meal, and it helps with the digestion, absorption, and processing of the food ingested.
Another common issue with temperature and the spawn is improper substrate ratios. Using too little spawn will lead to slow colonization, and using too much can cause mycelium to produce excess heat through a process called thermogenesis, which can cook the substrate and damage mycelium. Having the right amount of spawn in your substrate is critical for optimum growth, and you should research what ratios are best for each type of mushroom.