Following a mushroom bloom in the San Francisco Bay Area in late 2016,14 people consumed a poisonous fungus and fell drastically ill. One child even suffered permanent neurological damage. These were just some of the latest in a string of poisonings over the past few decades — a small handful of which proved to be fatal. The toxic cause: Amanita phalloides, better known by its grim moniker, the "death cap" mushroom.
Amanita phalloides is what's known in the world of mycology as a "mutualist," according to Anne Pringle, the Letters and Science Rubenstein Professor of Botany and Bacteriology at the University of Wisconsin-Madison. "A mutualism is, very simply, a relationship between two organisms of different species that result in a benefit for both organisms," says Pringle. As an ectomycorrhizal fungus (a fungus that grows outside the plant's roots), the death cap mushroom forms this relationship with a host tree. The fungus grows in the soil and mingles with the tree's roots, drawing out nitrogen from the soil and bringing it to the tree in exchange for carbon.
In California, where the death cap mushroom is fairly common — possibly due to its pleasant Mediterranean climate — the fungus normally grows in tandem with coast live oak. On the east coast, the fungus usually attaches to pine. And in the fungus' native Europe, it's a combination of beech and oak.