Produce Spotlight: Mushrooms

Diving into the food safety considerations of mushrooms.

Photo by Willie Crosby / Small Farms Quarterly

Produce Safety Spotlight: Mushrooms!

The edible mushroom market is a billion-dollar industry in the United States, and is covered under the FSMA Produce Safety Rule, the same as other fresh produce.

Recalls, Outbreaks, and Misidentifications of Mushrooms

One of the earliest documented outbreaks tied to mushrooms occurred in the United States in 1989. Four separate outbreaks of Staphylococcus aureus were traced to canned mushrooms imported from China. In total, an estimated 99 people became ill, with 18 hospitalizations. These outbreaks resulted in multistate recalls and an FDA order to restrict all mushrooms imported into the U.S. from the People’s Republic of China.

In more recent years, 2020 and 2022 each saw a multistate outbreak of Listeria monocytogenes in enoki mushrooms, a popular Asian specialty mushroom. The 2020 outbreak involved 36 total confirmed illnesses, 31 hospitalizations, and 4 deaths across 17 states. The 2022 Listeria monocytogenes outbreak spanned 4 states and had 5 confirmed cases, all of which were hospitalized. Since these two outbreaks, over 20 advisories and recalls have been issued for potential Listeria contamination. 

Another major source of mushroom-caused illnesses is the misidentification of wild mushrooms. The most extreme example of this occurs in China, which has reported thousands of mushroom poisoning outbreaks since 2010. There was also a notable case of misidentified toxic mushrooms in California this year. In most cases, the mushroom in question was a close lookalike of an edible variety, which emphasizes the importance of foraging education.

Risk Profile: What Makes Mushrooms Risky?

The dangers of wild, inedible mushrooms are well known, but it is important to remember that just because a mushroom species is edible, it is still not immune to food safety risks. Growing practices will affect the types of food safety risks, so let’s look at some possible differences between log-cultivated and substrate-cultivated mushrooms.

Log-Cultivated Risks

• Surface contamination of the logs where the plugs/caps are grown

• Cross-contamination related to the placement and storage of logs

• Exposure to outdoor elements such as wildlife and rain splash

• Quality of the water used to soak logs for irrigation

  
  

Substrate-Cultivated Risks

• Quality control of substrates, including pasteurization effectiveness

• Dense indoor production may amplify cross-contamination risks

• Pathogen persistence in damp grow rooms

• Cross–contamination during harvest and post-harvest activities

  
  

Regardless of the cultivation process, all mushroom growers should be mindful of the fact that humans are a major source of spreading human pathogens! Handling, harvesting, packaging, and all other human contact can introduce potential contamination if proper worker hygiene and sanitation are lacking. Likewise, equipment and food contact surfaces also need to be cleaned and sanitized diligently to prevent crop contamination.

Recommendations

First, always remember that food safety risks and hazards are inherent in growing crops, mushrooms included. Risk management is the key to good food safety! Even small actions can add up to big food safety benefits. Here are a few practices mushroom growers can implement to help protect the microbial food safety of their product.

• Review commodity-specific guidelines. The United States Department of Agriculture (USDA) offers a mushroom-specific Good Agricultural Practices guide. This voluntary audit is aligned with the minimum food safety standards provided in the Produce Safety Rule regulation.

• Training, training, and more training. Workers who learn and understand the basic principles of food safety will make better food safety choices.

• Monitor and manage water quality. Water is a known spreader of bacteria and pathogens. Ensuring clean water is important in all mushroom production, but especially in log-grown mushrooms, where the logs are typically submerged in water and soaked for multiple hours at a time.

• Ensure safe substrates. If purchasing substrate from a supplier, ensure it has been properly pasteurized or sterilized to kill all pathogens. If the substrate is made on-farm, take the necessary steps to sterilize it before use.  

Want to learn more?

Michigan Produce Safety Technicians are ready to help you meet your on-farm produce safety goals. We will work with you to identify, manage, and minimize risks to food safety on your farm, and help you create a comprehensive food safety plan to prepare you for an MI Produce Safety Risk Assessment Certificate. Working with produce safety technicians is always free and confidential, and there is no cost to apply for the certificate. Click here to get started.

Sources

1. Associated Press (2025, December 6). California officials warn against foraging wild mushrooms after deadly poisoning outbreak. U.S. News. https://apnews.com/article/poisonous-wild-mushrooms-california-monterey-san-francisco-cba09ed69bdd26450ee24cb5518efaba.

2. Centers for Disease Control (2022, November 17). Listeria Outbreak Linked to Enoki Mushrooms - November 2022. Listeria Infection (Listeriosis). Retrieved September 15, 2025, from https://www.cdc.gov/listeria/outbreaks/enoki-11-22/index.html.

3. Levine, W. C., Bennett, R. W., Choi, Y., Henning, K. J., Rager, J. R., Hendricks, K. A., Hopkins, D. P., Gunn, R. A., & Griffin, P. M. (1996). Staphylococcal food poisoning caused by imported canned mushrooms. The Journal of infectious diseases, 173(5), 1263–1267. https://doi.org/10.1093/infdis/173.5.1263

4. Li, W., Pires, S. M., Liu, Z., Liang, J., Wang, Y., Chen, W., Liu, C., Liu, J., Han, H., Fu, P., & Guo, Y. (2021). Mushroom Poisoning Outbreaks - China, 2010-2020. China CDC weekly, 3(24), 518–522. https://doi.org/10.46234/ccdcw2021.134

5. U.S. Food and Drug Administration (2020, June 9). Outbreak Investigation of Listeria monocytogenes: Enoki Mushrooms (March 2020). Outbreaks of Foodborne Illness. https://www.fda.gov/food/outbreaks-foodborne-illness/outbreak-investigation-listeria-monocytogenes-enoki-mushrooms-march-2020

6. U.S. Food and Drug Administration (2023, July 19). Investigation of Illnesses: Morel Mushrooms (May 2023). Recalls, Market Withdrawals, & Safety Alerts. https://www.fda.gov/food/outbreaks-foodborne-illness/investigation-illnesses-morel-mushrooms-may-2023.

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Article by Landen Tetil, Produce Safety Technician