Toxic Fungi of Western North America

by Thomas J. Duffy, MD

History of Amanita ocreata and Amanita phalloides in the West

In 1909, Charles Horton Peck described Amanita ocreata Peck from Pasadena, a white species. Peck recognized this species as distinct from the white form of Amanita phalloides (Fr.:Fr.) Link. var. alba Britzlem. Amanita phalloides and Amanita ocreata react differently with KOH. Amanita ocreata turns yellow with a drop of KOH solution. Amanita phalloides does not.

Harkness and Moore in their "Catalogue of Pacific Coast Fungi" published by the San Francisco Academy of Sciences in 1880 reported a collection of Amanita phalloides from San Rafael, a city in Marin County just north of San Francisco. However, Dr. Roy Hallings searched six bins of Harkness material now located at the New York Botanical Garden and could find no Amanita phalloides. A March 1884 A.J. McClatchie collection from Oak Knoll in Alameda County (east of San Francisco) labeled Amanita phalloides was Amanita ocreata. (2) William A. Murrill reported Amanita phalloides from Western North America in 1912. (6) These collections from Santa Cruz, California, were white to pallid mushrooms and appear to have been Amanita ocreata. Murrill was careful to note that he did not see any fresh material. It was a Professor Campbell at Stanford that originally thought the local species was a white form of Amanita phalloides.

Dr. Alexander H. Smith was the first to authenticate a US identification of Amanita phalloides in his first edition of "The Mushroom Hunter's Field Guide" published in 1958. This 1957 collection was from San Mateo County just to the South of San Francisco, but it later turned out not to be the oldest authenticated collection. The earliest correctly identified collection of Amanita phalloides in the United States goes back to November 2, 1938 and is in the herbarium of the University of California, Berkeley(2). Dr. Isabel Tavares authenticated this collection, which came from the garden of the Del Monte Hotel in Monterey County and was found fruiting under an imported shrub. The oldest authenticated collection of Amanita phalloides under a native tree (Quercus agrifolia, "coast live oak") was found at Observatory Hill near the Main Library, University of California, Berkeley Campus on December 31, 1945. (2)

Amanita phalloides
Amanita phalloides photo © Fred Stevens

Dr. Harry Thiers, shortly after coming to San Francisco State University in 1959, noted specimens of Amanita phalloides in association with coastal live oak in three "bay area" counties—San Mateo, Santa Cruz, and Alameda. San Mateo and Santa Cruz Counties are south of San Francisco; Alameda County lies across the bay east of San Francisco. The first survey of Amanita phalloides in California (1963-1968 by Gary Breckon) suggested that Amanita phalloides was relatively uncommon. By 1970 massive fruitings sporadically occurred in San Francisco Bay under live oak.

Dr. Fred Stevens, one of Dr. Thiers’ students, noted repeated San Mateo fruiting with cork oak, a tree that Dr. and Mrs. William Freedman had found to have been planted by the San Francisco Water Department in 1943 and 1944 directly from European seedlings. The hypothesis was that Amanita phalloides from cork and other European oaks may then have adapted and transferred to California live oak rootlets, accounting for some of the increased sightings. Greg Wright in Southern California also reported Amanita phalloides in association with coastal live oak in Santa Barbara and later in Los Angeles. (7)

Because of these two common fungi, the large population and an influx of immigrants, California currently leads other North American states or provinces in mushroom fatalities. The first recorded US fatality, however, was on a New York tombstone for William Gould, his wife and son in 1838: “Poisoned by eating Fungi (toadstools)”. (11) The first supposed “mushroom” death in California was reported from Chico in 1871, but the symptoms suggest a plant or mixed poisoning rather than toxic fungi. (12) The oldest medical journal report comes from Boston in 1890. The mushroom that was the cause of death was certainly not the postulated “Amanita verna”, but most likely Amanita bisporigera G. F. Atk. or Amanita magnivelaris Peck. (13), (13a)