No one could have predicted the massive spread of golden oyster mushrooms in the United States.
The golden oyster mushroom, or Pleurotus citrinopileatus, seems like an innocent and edible fungi, but it has become a rapidly spreading, invasive species throughout the central and northeastern United States.
In the last 15 years, it has been found in moist woodlands throughout Missouri, especially the upper part of the state and in Boone County.
Golden oysters grow on hardwoods so quickly that they aggressively eliminate native fungal species and severely damage the natural balance of forest ecosystems.
The fungi are native to Asia and were brought to North America in the early 1990s for commercial culinary purposes before they escaped into the wild to compete with other fungi for dead hardwood.
The continued cultivation of the golden oyster mushroom, coupled with the billions of spores it releases, is at the root of their expansion.
“Losing that biodiversity potentially means disrupting nutrient cycling, disrupting relationships with other organisms and disrupting wood decay,” said Aishwarya Veerabahu, a doctoral student at the University of Wisconsin-Madison doing research on golden oyster mushrooms.
Veerabahu’s project is split into three segments — ecological impact, stakeholder perspectives on what to do going forward and a genomic study to uncover the traits that make the spread of the golden oyster mushroom so successful.
By drilling into dead elm trees in the Madison area, Veerabahu’s team found that trees hosting golden oyster mushrooms had far fewer fungal species compared to trees without golden oyster mushrooms.
Veerabahu said despite the negative impacts of invasive fungi, they are seldom noticed by the public to the degree that invasive plants are.
Ari Jumpponen, a mycology professor and researcher at Kansas State University, said the golden oyster mushroom is far from the first invasive fungi to pose a threat to native wildlife.
Jumpponen said the damage of invasive fungi is largely irreversible once introduced.
“This is one of those examples where we have actually transported a foreign organism into our continent and it has taken off,” he said.
Some fungi, like the Dutch elm disease, a fungal pathogen that has killed massive amounts of elm trees in the United States, and chestnut blight, which decimated the American chestnut tree, have been introduced accidentally before spreading wildly out of control.
Kits for growing mushrooms have been sold for years to those interested in trying their hand at cultivating fungi. The danger is that these fungi could spread farther than intended.
“We all like to be adventurous and try new foods, try new vegetables, put new ornamentals outside our house,” said Steve Buback, state botanist with the Missouri Department of Conservation. “Every time we do that, we’re rolling the dice.”
Veerabahu said commercial growers are aware of these risks and are looking for solutions. A sporeless strain, for example, would not completely mitigate the risk, but would make it more difficult for the mushroom to spread.
The key is prevention: There isn’t anything to stop the mushroom from spreading right now, and the most important takeaway is the broader picture on preventing invasive, non-native mushrooms from spreading in the first place, Veerabahu said.
“This story is not about the golden oyster mushroom,” she said. “(It's about) putting up a flag for other invasions that might happen in the future.”
