GCK Mushrooms with FloCube and petri dishes

Common Causes of Mushroom Contamination and Early Warning Signs

Image above is a submitted photo by FloCube customer GCK Mushrooms 

As a mycologist, it’s important to identify early signs of contamination on your mushrooms. It’s imperative to keep a close eye on your growing environment so you can take corrective measures before the contamination spreads and causes damage to your entire mushroom crop. Learning the common causes of mushroom contamination and early warning signs is critical for a successful harvest.

Where do the contaminants come from?

Put simply, contamination occurs when unwanted microorganisms invade the growing environment and compete with the mushrooms for resources. This can result in reduced yields, poor-quality mushrooms, and even the loss of an entire crop. No one wants that. Here are some of the main sources of mushroom contamination to keep in mind.

Poor hygiene:

Poor hygiene is one of the most common causes of contamination in mushroom cultivation. If the growing environment is not kept clean and sanitized, it can become a breeding ground for harmful bacteria and fungi. It’s important to sterilize all equipment, tools, and surfaces before and after use to prevent contamination. Read my blog on sterilization here >>


Inadequate ventilation

Proper ventilation is essential in mushroom cultivation. I can not say that enough. Without adequate ventilation, the growing environment becomes humid and stagnant, creating a breeding ground for contaminants. Proper airflow with the use of a FloCube flow hood helps to regulate temperature and humidity levels, preventing the growth of harmful microorganisms. Read our blog on why flow hoods are critical for serious mushroom farmers.

Poor quality spawn or substrate

If the spawn or substrate used in mushroom cultivation is of poor quality, it can be more susceptible to contamination. It is important to use high-quality spawn and substrate to ensure healthy mushroom growth and reduce the risk of contamination. Spend a couple of extra bucks and get high-quality materials for your mushrooms. It’s critical to pasteurize or sterilize your substrates to ensure you are working with a clean substrate. Read more about Contamination From Substrates 

Insects and pests

Insects and pests can introduce harmful microorganisms into the growing environment. It’s essential to regularly inspect your grow room for signs of pests and take appropriate measures to rid them from your workspace.

Oyster mushroom graphic

What are early warning signs of mushroom contamination?

Being able to identify the signs of contamination in your growing environment is crucial for the success of your crop. Regular monitoring and taking corrective actions promptly help prevent the spread of contamination on your mushrooms.

  • Foul odor: A strong and unpleasant odor is a clear indication of contamination in the growing environment. 
  • Discoloration: If you notice any discoloration on your substrate or mushrooms, it could be a sign of contamination. This discoloration can range from yellow, green, or black spots.
  • Mold growth: If you notice any white or green fuzzy growth on your substrate or mushrooms, it could be mold.
  • Slimy texture: A slimy texture on your substrate or mushrooms is a sign of bacterial contamination. 
  • Stunted growth or abnormal morphology: If you notice that your mushrooms are growing abnormally or are stunted, it could be a sign of contamination.

3 Common Causes of Mushroom Contamination

Airborne contamination

Airborne contamination can be caused by various factors, including poor ventilation, proximity to a contaminated area, and outdoor contamination. In indoor mushroom cultivation, poor ventilation can cause a buildup of carbon dioxide and humidity, which can create an ideal environment for the growth of harmful microorganisms. This is especially true if the growing area is not well-sealed or if there are gaps in the doors or windows. Using a FloCube flow hood with HEPA filters takes the stress out of worrying about airborne contaminants so you can focus on your research.

Equipment contamination

Equipment and tools used in mushroom cultivation can also be a source of contamination. Tools that are not properly cleaned and sanitized can harbor harmful microorganisms that then spread to the growing environment. Be sure to sterilize everything and keep a clean workspace for your mushrooms. We have lab-quality stainless steel tables, flow hoods, HEPA filters, and sterilizers available in our shop for the best price on the market.

Human contamination

Human contact can also be a source of contamination. Hands, clothing, and other personal items can introduce microorganisms into the growing environment. It is important to practice good hygiene and wear appropriate clean clothing when working with your mushrooms. Be sure to change into clean clothes, clean shoes, wash your hands, and tie your hair up to reduce the risk of any contaminants coming in contact with your growing mushrooms.

As a mycologist myself, I understand that contamination is a big concern for those who are growing mushrooms.

I encourage you not to worry too much about contamination and to focus on learning the techniques and methods for successful mushroom cultivation. Working with our lab quality  mushroom cultivation equipment, FloCube lets you focus on your research.


Keep in mind that contamination is a risk in any type of agriculture. By taking the necessary precautions outlined above and following proper procedures, the risk of contamination can be minimized. If you’re at a point where you’re ready to invest in your mushroom cultivation equipment and looking to buy a lamiar flow hood, We offer the most affordable lab-grade mushroom equipment on the market. 

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