Deadly Mushrooms 

Foraging for mushrooms? Don’t die. 

That’s the message from California Poison Control this winter. Thirty-five people have gotten sick so far this season after consuming death cap mushrooms they mistook for edible varieties. Three of the victims needed liver transplants to survive. Three died. The current epidemic of mushroom poisonings unfortunately also includes dogs, although fatality numbers were not provided.

“We anticipate that these mushrooms could continue to be fruiting in abundance throughout the rainy season in California,” said Dr. Craig Smollin, medical director of the San Francisco division of the California Poison Control System.

So far, all of the cases have been in Northern and Central California, but officials warn that death cap mushrooms can be found throughout the state, and with the increasing popularity of mushroom foraging, the risk of more incidents is high. 

In a typical year there may be only three to five cases of mushroom-related poisoning. This year, early rains and warm weather have generated a “super bloom” of mushrooms, including unusually abundant numbers of the highly toxic death cap mushroom, Amanita phalloides.

Death cap mushrooms prompted the current warnings, but a related species, the Western destroying angel mushroom, is also highly toxic and abundant this year. Toxic amanita species account for the vast majority of fatal mushroom poisonings in humans and animals. Some estimates are as high as 90-95 percent. 

The most potent mycotoxin in death cap and destroying angel mushrooms is amanitin, an amatoxin (both named for the genus Amanita) that attacks the victim’s liver and kidneys. The death rate for those who ingest either species is high—between 60-80 percent. Advances in medicine, including life-saving organ transplants, have helped to increase the odds for victims of this type of mushroom poisoning, but those odds still aren’t great, and medical intervention can only help if the patient realizes what is happening and seeks emergency help quickly. 

The initial gastrointestinal symptoms are violent and unpleasant, but the lethal damage can go unnoticed until it is too late, quietly destroying the liver and kidneys. Those who survive the experience, even the ones who do not require an organ transplant or dialysis, may face a lifetime of complications from organ and GI tract damage. 

Why would anyone ever eat a poison mushroom? Unless murder is on the menu, mushroom poisoning is almost always a case of mistaken identity. The killer mushrooms are similar to a number of benign, edible species, including several non-toxic species of amanita but also some of the edible species of the genus Agaricus—field mushrooms similar to the ordinary white button mushrooms grown commercially. Young death cap mushrooms can also look similar to edible puffball mushrooms, and at least one poison survivor mistook destroying angel mushrooms for edible shaggymane inkcap mushrooms. Mushroom ID can be complicated and even experts can make mistakes. 

For the casual mushroom enthusiast who depends on search engines and social media for identification, mistakes can be deadly, and AI makes the issue even more perilous by delivering unreliable results that misidentify mushrooms, or provide potentially inaccurate information about them. 

The unscrupulous, attempting to cash in on a potentially lucrative market, are using AI to generate guidebooks illustrated with AI generated mushroom images that may have no or little basis in reality. A quick search for information on edible mushrooms in the Santa Monica Mountains using Google AI turned up a host of questionable AI-generated material.

How can one be sure that the mushrooms one gathers are safe to eat? It’s a good idea to avoid all wild white mushrooms, unless they have been ID-ed by a real live human expert, and sometimes even experts make mistakes. 

The destroying angel is a pure white mushroom. The death cap is mostly white but may be slightly yellow or green. They both grow from an egg-like volva, which can be hidden underground or broken off. Young mushrooms often display an annulus—a ring around the stipe or stalk, but that, too, can fall off, and some of these species’ edible lookalikes also have rings.

Both deadly amanita species produce white spores, while many of the edible species they resemble produce dark spores, but this can be difficult to differentiate when mushrooms are young and the spores have not yet matured. Taking a spore print by placing a mushroom cap on a piece of paper, covering it with a bowl, and leaving it overnight, is the best way to check this attribute. However, few mushroom foragers intent on harvesting succulent mushrooms for dinner are likely to take the time before cooking and eating their haul, and it only takes one half of a death cap or destroying angel to kill a full grown adult.

Amanita ocreata, the Western destroying angel, is a native species, one that is common under Topanga’s oaks. It’s considered to be the most toxic North American member of the Amanita family. A. phalloides, the death cap, is an unwelcome invasive from Europe that has spread throughout the state in recent years. It is even more toxic than its native cousin. These mushrooms are beautiful, with their classic fairytale shape, but they are by far the most potentially deadly life form in the Santa Monica Mountains. The odds of surviving a rattlesnake bite are far higher than surviving amanita mushroom poisoning. 

Death caps and destroying angel mushrooms are among the most toxic mushroom species in this area, but there are other poisonous mushrooms that can also cause serious problems if they are accidentally mistaken for edible varieties.

Many victims of Amanita mushroom poisoning have mistaken a death cap or a destroying angel for one of the edible species of Agaricus mushrooms, like Agaricus campestris, the meadow mushroom. However, it is also easy to mistake the poisonous Agaricus californicus for an edible field mushroom. There is enough mycotoxin present in this species to cause severe gastrointestinal distress and in some cases, liver or kidney damage.

The Western jack-o-lantern, Omphalotus olivascens, can look like the highly desirable California golden chanterelle, Cantharellus cibarius, but will cause nausea, vomiting, abdominal cramping, diarrhea, weakness and dizziness, and may also cause liver damage and sometimes even hallucinations.

Galerina marginata, a small, rubbery, brown mushroom that is almost as toxic and deadly as the poisonous amanitas and contains some of the same mycotoxins, can be mistaken for species of the psychedelic mushroom Psilocybe, sending the person consuming it on a very different kind of trip—either to the hospital or to the grave.

There are a couple of edible and highly desirable morel species in the Santa Monica Mountains, but even this well-documented edible mushroom can cause illness if it isn’t adequately cooked. Morels also have some potentially toxic lookalikes, including the elfin saddle mushroom, Helvella lacunosa, which contains the toxin monomethylhydrazine, a chemical that is also found in rocket fuel. 

Another morel lookalike that occurs in other parts of California may cause permanent, lasting neurological damage. Gyromitra esculenta, which contains the mycotoxin gyromitrin, can be lethal if consumed raw, but even cooked it may be problematic. Recent research suggests that gyromitrin poisoning may be linked to clustered outbreaks of Amyotrophic Lateral Sclerosis (ALS) in parts of Europe where this mushroom is consumed.

The mycotoxins that occur in poisonous mushrooms are thought to have evolved to protect the organism from predation. Some of the most deadly mushrooms contain multiple mycotoxins of varying potency and how they work is still not fully understood. Some animals can eat poisonous mushrooms with no ill effect—slugs seem to thrive on death cap mushrooms. Some humans are sensitive to even the most commonly available commercial mushrooms—a condition known as fungus-food allergy syndrome, or FFAS. Others can eat all kinds of edible mushrooms and fungi-containing foods with no ill effect. 

The edibility of a surprising number of wild mushrooms is unknown or variable. Chicken of the woods, Laetiporus sulphureus, is a good example. This bright yellowish-orange shelf fungus that grows on the trunks of trees is a favorite with foragers. Many people can eat this mushroom with no ill effect, but for the unlucky minority, they cause violent cramps, nausea, diarrhea and vomiting. 

Even edible wild mushrooms need to be handled with care and knowledge. Some mycotoxins are neutralized by cooking; some, like the deadly amatoxins, are not. Some mushrooms can only be safely eaten when they are young, or if they are growing in a particular kind of substrate, or after being boiled in several changes of water. 

Mushrooms can be edible, medicinal, hallucinogenic, or deadly, and species with those qualities grow right here in our gardens, along the roadside, in our parks. The one thing almost all of them have in common is that they are extremely ephemeral, appearing after a rain, and vanishing almost as quickly. 

Foraging is increasingly popular but our mountains are a small island of habitat and the number of places available to forage are limited. Removing anything from state or federal parkland in the Santa Monica Mountains is illegal. Humans have the option of buying sustainable mushrooms at the farmers market or the store, the wildlife does not, and this is an unforgiving hobby, one where mistakes can result in an agonizing and slow death. Right now, when some of the most toxic mushrooms are unusually abundant, state officials are asking the public not to forage for mushrooms. Not this year. In the words of the late British writer Sir Terry Pratchett, All fungi are edible. Some fungi are only edible once. Anyone who suspects that they have ingested a potentially poisonous mushroom of any kind should immediately contact poison control. Speedy treatment is essential. https://calpoison.org/