Amanita muscaria var. guessowii

Amanita muscaria var. guessowii in eastern Canada

Amanita muscaria var. guessowii is the common, bright yellow and/or yellow and orange fly agaric of eastern North America. The European name A. muscaria var. formosa Pers. has been mistakenly applied to this taxon. Some macroscopic dimensions in the following are taken from (Jenkins, 1977).

This variety apparently contains the same toxins as Amanita muscaria (L. : Fr.) Lam. subsp. muscaria of Europe, northern Asia, and far northwestern North America (western Alaska). With the recent large increase in immigration from Mexico into the eastern half of the U.S., we have seen an increase in poisonings by var. guessowii because it is mistaken for the edible Amanita basii Guzmán & Ramírez-Guillén (until recently, called "Amanita caesarea" by Mexican authors). When diagnosing the poisoning by questioning a Spanish-speaking victim, it is important not to simply translate "amarillo" as "yellow." One of the common names of Amanita basii in Mexico is "amarillo." A poisoning victim recently immigrated from Mexico to the eastern U.S. may be conveying the name of the mushroom by the word "amarillo," not just the color of it.

Amanita muscaria var. guessowii is associated primarily with conifers, but can occur with deciduous tree genera as well. It often occurs in the Fall in the mid-Atlantic states of the U.S., but it may appear as early as May in years with plentiful Spring rains. The northern limit of the range of this taxon is north of the Isl. of Labrador and central Quebec. The southern limit is not clear to me, but the range certainly includes the central Appalachian region. Other American taxa currently treated as varieties or subspecies of A. muscaria are A. muscaria var. alba Peck, and A. muscaria subsp. flavivolata Singer.—R. E. Tulloss

22/10/2021 Québec, Canada

Photos are taken by me.