By Kathlean Wolf
Wild Warner
In 2018, I spotted a bright yellow mushroom growing on a dead tree in the Old Warner Woods on the east side of Warner Park. We’d had two very wet years in a row, prompting hundreds of fungi to form mushrooms, and I’d spent those years photographing as many fungi and protists (slime molds) as I could. This mushroom I had never seen before. I took its picture, harvested it, and took it home to identify and research.
The new species was the golden oyster mushroom, Pleurotus citrinopileatus, a prized edible mushroom native to eastern Russia and northern Asia. Golden oyster mushrooms were brought into the United States deliberately, including for use in grow kits for backyard mushroom farmers.
By 2022, I was certain the golden oyster must be an invasive species. Logs I’d once visited to harvest chicken of the woods mushrooms were no longer producing those delicious and beautiful native edibles. My favorite fungus, an inedible, incredibly beautiful mushroom that looks like a coral reef in miniature, disappeared altogether.
Instead, these logs produced bloom after bloom of golden oysters, and the wood broke down far more quickly than normal. This rapid breakdown left less soil-cover, and fewer homes for insects and small animals. Worse still, the golden oysters appeared at the top of dead ash trees; the height of these standing trees allows the mushroom spores to travel far and wide.
In June of last year, my question was answered by researchers at UW-Madison in a paper published in the journal Cellular Biology. Researcher Aishwarya Veerabahu and her team found that the number of different fungi in wood colonized by golden oysters was reduced by 60%, and the species that remained were different than the species that had been there before.
This loss of fungi has many potential impacts both for the web of life and for human beings. The mossy maze polypore fungus has a symbiotic relationship with woodwasps, a type of stingless wasp also called horntails. When golden oysters eliminate this fungus, woodwasps are likely to see a steep decline. Elm oysters, a unique edible found in box elder trees, have a genetic code that could lead to significant medical discoveries.
While it’s fun and educational to grow your own mushrooms from a kit, the risk to the ecosystem isn’t worth the potential harm. I remember seeing golden oyster logs growing in the backyard of a friend in the 2010s and thought nothing of it. In hindsight, the question of invasiveness should have been asked long before the spores were brought to our shores.
One other lesson of this invasion is the impact of community science. Before golden oysters were identified as a harmful organism, the sightings that prompted the study of their invasion came not from formally trained scientists, but from ordinary folks walking through woodlands and recording their observations.
Becoming a community scientist is as easy as searching the web for things that fascinate you. Two popular apps and websites are eBird and iNaturalist. Your contributions may be the ones that sound the alarm about a new hazard — or in some cases, good news about the recovery of a formerly imperiled species.
Learn more: Invasive Golden Oyster Mushrooms Are Crowding Out Native Fungi and Could Slash Biodiversity in Forests (https://tinyurl.com/goldenoysterstudy).
