Poisonous Fungi
Growth stages of Amanita phalloides (death cap)
Photo credit: David Rust, President of the North American Mycological Association
Doubtless as soon as people learned by experience that fungi could serve as food, they found also that some were poisonous. To many, the very word fungus suggests something mysterious, something morbid. It was comparatively easy to describe herbs, shrubs and trees clearly enough for them to be recognized; indeed, many of the old names are still used. But toadstools are for the most part short-lived and irregular in occurrence and their distinguishing characters are not very easy to grasp. Consequently, instead of clear descriptions of those species which were known to be safe and those which are dangerous, various rules were given for distinguishing the two groups. These rules were repeated by the herbalists and many of them have a world-wide relevance even today. The primary division into edible and poisonous species influenced the classification of fungi until comparatively recent times.
Many types of foods can be somewhat indigestible when over-indulgence becomes an issue, even Fungi, and consequently a certain discretion is advisable concerning the time and the amount to be eaten. There are, however, some species of Fungi which are especially indigestible. One noteworthy example is the Yellow Staining Mushrooms (Agaricus xanthodermus). Some other species are also very indigestible, though the gastro-intestinal effects they produce in some people may be due to specific resinoid substances which act on the mucous lining of the intestine. This is certainly so with Entoloma lividum where the symptoms are very severe and may be fatal. Several species which cause purging were formerly held in high esteem. The other poisonous species may be classified as:
1. Those containing substances which after a long incubation period bring about the degeneration of the cells of the body (especially the kidney and liver): Amanita phalloides, Amanita verna and Amanita virosa are deadly. The rare Lepiota helveola belongs to this group but is less dangerous.
2. Those containing substances which can cause paralysis to the nervous system: Amanita muscaria, Amanita pantherina, and Inocybe patouillardi.
3. Those containing substances which destroy the red blood cells: Gyromitra esculenta
An expression frequently used is that certain mushrooms ‘look poisonous’. This usually refers to color, though sometimes it is shape or structure. Bright colors are most often supposed to be danger signals, but all colors except white, cream or pale yellow arouse suspicion (there are a lot of very, very poisonous white mushrooms as well, such as some of the Amanitas above). Color, however, is of no significance of itself in determining whether a fungus is poisonous or not; its importance lies in its being one of the main characters which distinguish one species from another. Similarly, with shape and structure. The Field Mushroom (example: Agaricus) is presumably taken as the model by which all other species are judged, so the more a fungus differs from this pattern the more likely is it thought to deviate from perfection as food. Whatever the shape or structure of a mushroom, whatever it reminds one of, are not of the slightest value in determining whether it is wholesome.
There is a great range of odors among mushrooms. Many species have the odor of fresh meat; a few smell like old rancid meat. Several species have the offensive smell of bedbugs. A good sniff is needed to detect what odor there is; sometimes, however, it is noticeable anywhere in the neighborhood of the fungus; occasionally it is necessary to bruise or cut a specimen for it to become manifest. Dried specimens often retain their special odor for many years. It might be thought that smell would give a clue to edibility, but unfortunately this is not so. None of the British poisonous species has an unpleasant smell and the deadly poisonous species of Amanita are odorless.
It has been a common belief from earliest times that if the flesh of a fungus changes color when cut or broken, it is poisonous. Some species of Boletus, e.g. Boletus luridus, almost instantly become a vivid blue when broken; other fungi become reddish, yellowish, or blackish and the ‘milk’ of some species of Lactarius gradually changes color. None of these color changes is of any significance in denoting the presence of poisonous substances.
No reliance should be placed on the fact that a species is nibbled on by some animal or other. Rabbits for example, are not usually affected by Amanita phalloides, simply because their stomach contents are able to neutralize the poison.
All other tests are similarly useless, such as that edible fungi grow in fields and not in woods, in grass and not on or under trees, occur early in the season and so on. No rule-of-thumb method is safe. Indeed, by everyone of the usual tests the deadly poisonous Amanita phalloides, Amanita verna and Amanita virosa would be considered perfectly safe, whereas the Field Mushroom would give rise to doubts.
So, how to tell the difference between poisonous and edible mushrooms? The answer is simple you can’t tell the difference without identifying the individual mushroom you have found. However, some good rules apply to avoiding poisonous mushrooms;
1. Avoid mushrooms with white gills, a skirt or ring on the stem and a bulbous or sack like base called a volva.
2. Avoid mushrooms with red on the cap or stem.
3. Don’t consume any mushrooms unless you are 100% sure of what they are.
These 3 rules don’t mean all other mushrooms are safe, but they do help rule out some the nastier types. You may be missing out on some good edible fungi by following these rules, but the goal is in turn you will be avoiding the poisonous ones.
Be safe and happy hunting!
** Gourmet Mushroom Inc. does not deal in production or sales of any wild mushrooms and customers with any fear of wild mushrooms should seek the safer cultivated varieties, in which we offer at GMI.
Written by: Sonya Lague
Mushroom Grower/Data Entry Specialist
Gourmet Mushrooms Inc.