Tom Volk's Fungus of the Month for August 1999

This month's fungus is Chlorophyllum molybdites, the green spored Lepiota

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Chlorophyllum molybdites fairy ringTo the left is a fairy ring of this month's fungus, Chlorophyllum molybdites. Fairy rings got their name in the olden days in Europe, when people came upon these rings of mushrooms in clearings and meadows in the woods. Obviously there must have been some fairies or wood nymphs doing their magical dances during the night in and out of these fairy rings. Now before you make any value judgments about the fairies in the ring in this picture, let me tell you about the people I forced to do this. Both are former undergraduate students in my Mycology class the last time I taught it at the University of Wisconsin-Madison in Fall 1994 (as a temporary substitute-- it was the seventh time I had taught Mycology in the Botany Department there). On the left is Dan Czederpiltz, now in graduate school in Plant Pathology/Mycology at the UW-Madison and on the right is Kelly Collins, now in graduate school in Plant Pathology/Mycology at Oregon State University. I am now happy to count them both among my most important mycological colleagues.Chlorophyllum molybdites with Kelly's legs

Anyway back to the fairy rings-- how and why does a fairy ring form? Think for a minute about the way a fungus grows on a piece of bread on your countertop-- the colony is very circular, with the fungus spreading out in two dimensions on the top of the bread. Grassy lawns are a fairly homogenous substrate and the mushrooms often grow in rings. The colony of the Chlorophyllum must have been inoculated in the center several years before. Usually the center of such colonies dies and the only living part is around the outside edge, where the fruiting bodies can form. Other mushrooms that often form fairy rings in lawns include Agaricus campestris, Calvatia cyathiformis, or *the* fairy ring mushroom, Marasmius oreades. It's a little more complicated for a fungus in the woods. The substrate is not so homogenous. You can see Calvatia gigantea forming fairy rings in the deep woods as the August 1998 Fungus of the Month.
Chlorophyllum molybdites and Lepiota rhacodes fruiting bodiesThis month's fungus is very abundant and is among the most common causes of poisoning in North America, especially in the South, Pacific Northwest and California. Apparently it has a worldwide pantropical distribution. I often think of this as a southern fungus, but with the hot and wet weather here in the upper midwest, we found this mushroom in La Crosse recently- last year we even had our own local poisoning. But why should this fungus cause more problems than any other?

Chlorophyllum molybdites closely resembles two edible Lepiota species. In the picture, the poisonous Chlorophyllum molybdites is on the left and the delicious edible mushroom Lepiota rhacodes is on the right. Several other edible Lepiota species can also be confused with Chlorophyllum molybdites, including the parasol mushroom Lepiota procera, and also Lepiota americana. In case you're looking for these in a field guide, some authors include these species in the genus Macrolepiota.

Chlorophyllum molybdites greenish gillsThe major difference between Chlorophyllum and Lepiota is that Chlorophyllum develops green tinted spores and a green spore print. In older specimens the gills often turn green also (hence the name chloro=green, phyllum=gills). However, often the spores take a while to mature and may even appear to be white as in Lepiota! There was a poisoning some years back in which a famous mycologist searched the entire fruiting body that had poisoned someone and could only find *one* green spore. Symptoms of Chlorophyllum molybdites poisoning are mostly gastrointestinal in nature. According to Dennis Benjamin (Mushrooms: poisonings and panaceas, 1995, W.H. Freeman and Company, 422 pp.) "in some individuals the gastrointestinal syndrome, which occurs about 1-3 hours after the meal, can be very severe, especially the colicky abdominal pain, which can mimic that of a 'surgical' abdomen. Symptoms persist for up to six hours, and even longer in a few patients. Nausea, vomiting and diarrhea complete the picture. The diarrhea can be explosive in nature and become bloody." You probably won't die from eating this mushroom (although there is one recorded fatality involving a child), but it's certainly not a pleasant dining experience--- So be very careful if you plan on eating any Lepiota species. Projectile diarrhea would not be very much fun.

Chlorophyllum molybdites specimensThe North American Mycological Association keeps a Mushroom Poisoning Case Registry for North America, which was organized to collect and provide information on mushroom poisoning in North America. Since 1983 the Registry has received reports of 1608 human (343 children) and 86 animal cases; 1013 with identified mushroom species. Reporting (from 47 states, DC, 6 Canadian provinces, Mexico) is voluntary and varies geographically- a factor in evaluating the data. Species most reported in human cases: Chlorophyllum molybdites, 135; Amanita pantherina, 76; Amanita muscaria, 72; Omphalotus olearius, 55; Armillaria mellea, 40; Laetiporus sulphureus, 34; Amanita verna/virosa, 33; Gyromitra esculenta, 32; Amanita phalloides, 29. [Information from the NAMA Toxicology Committee, Kenneth W. Cochran, John H. Trestrail, III] Click here for more information and a form for reporting mushroom poisonings.
I hope you enjoyed learning something about Chlorophyllum molybdites . Please be careful when you're eating any kind of mushroom. It may be tempting because of the large size and abundance of this mushroom-- it even tastes pretty good according to those who have tried it. but after a few hours with most people the gastrointestinal upset come on, and you'll regret eating this mushroom.

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