Know Your Enemy

Common poisonous AZ mushrooms and lookalikes of edible mushrooms

There are many ways in which one may appreciate and enjoy the wonders of the fungal kingdom. Amateur mycologists take an academic approach and are interested in identification, classification, and ecology. Nature photographers focus on the aesthetic appeals of these exotic, ephemeral mycoflora. And, as you know, wild mushrooms have broad appeal for mushroom hunters. It is the subject of edibility, and the concern over extreme inedibility, that brings you to this section.

In general, very few mushrooms contain toxins that are deadly poisonous. But, on the flipside, many, many mushrooms can be sickening. Additionally, those mushrooms that are poisonous are often quite common. All this adds up to a very unpleasant equation for those who would undiscriminately pick mushrooms for the table. You simply must take care and be certain of your identities if you plan on eating anything you find. There is a well known mushroom hunter saying: "There are old mushroom hunters. There are bold mushroom hunters. But there are no old, bold mushroom hunters!" (Exception: Chuck Barrows)

I suggest taking the same approach as you would for eating wild plants / berries:
- Know the general groups of mushroom producing fungi.
- Know how to identify an unknown.
- Become familiar with the common edibles / inedibles in your region.

Below are some poisonous mushrooms and lookalikes of edible mushrooms that I think you should be familiar with. Remember that there are hundreds of inedible / sickening species of mushrooms here in Arizona. You are after the select few that can be safely eaten. It is up to you make educated, intelligent choices in what to bring back home.

Amanitas

As a mushroom hunter, you absolutely must familiarize yourself with the genus Amanita. Deadly Amanitas are the cause of the majority of mushroom poisoning deaths in the country. They grow large and the poisonous varieties often have a pleasant taste. They share some characters with the widely edible Agaricus, and some edible species of Amanita are collected by (very adventurous) mushroom hunters.

Other cultures, especially east Asian cultures, commonly collect Amanitas and their edible lookalike Volvariella (the paddy straw mushroom) in their home countries. Alas, poisonous North American Amanitas can resemble edible Asian varieties; you can guess the unfortunate results.

Amanitas are mycorrhizal; mostly with conifers. You will often find them in or at the edge of forests. While you may find Amanitas a stones throw away from the treeline, it is only because they are developing from the farthest reaches of the tree roots.

The key identifying features of Amanitas are:
- Long, straight stem
- Cap margin often striated
- Specialized base: typically bulbous and possibly scaly
-- Additionally at base, a sac called a volva is typically present
- Skirt connected at the top of the stem, typically present
- White spores on free gills (some species have colored gills)
- Almost always in the presence of conifers.
- Typically medium to large in size.

Please take a moment to page through an image search of the genus Amanita. Note the common characters of this stately mushroom. On your walks during mushroom season, try to find Amanitas and learn their appearance.

MushroomExpert.com has an excellent summary of Amanita characteristics and an identification key to some common species.

- The Western Destroying Angel (Amanita ocreata )

As a very general rule, any all-white mushroom should be looked at as suspect. Seasoned mushroomers will scoff at this, but such a guideline helps keep amateur foragers safe from this deadly Amanita.

Michael Kuo at MushroomExpert.com summarizes the destroying angel well:

The distinguishing features of [Amanita ocreata] are:

• The white "sack" around the base, known as a " volva ," resulting from the universal veil .
• The pure white gills, which are usually free from the stem.
• The stark white color of the entire mushroom.
• The smooth cap, which almost always lacks patches or warts.

Please refer to your mushroom ID guide and review the characters of this deadly Amanita. Details are also listed at MushroomExpert.com.

Amanita ocreata definitely occurs in Arizona. It is listed in the Arizona Mycota Project fungi of Arizona checklist, and I have encountered it in the southeast sky islands of Arizona.

Amanita ocreata from Mt. Lemmon. This photo has a yellow tinge, but the mushrooms were pure white.

- The Death Cap (Amanita phalloides)

The death cap is another deadly Amanita that occurs in Arizona. Unlike the destroying angel, this Amanita has a colored cap. In other ways, it is similar in size and appearance.

These are the main characters of the death cap:

• Volva sac is present
• Skirt is present
• Cap ranges in color. Typically greenish / olive.
• Cap margin lacks striation
• White gills, free from stem
• Stem is fairly thick and straight
• White sporeprint
• May be found with oaks.

For a more detailed description, check your field guide or visit the Amanita phalloides page at MushroomExpert.com.

Amanita phalloides definitely occurs in Arizona. It is listed in the Arizona Mycota Project fungi of Arizona checklist.

Agaricus xanthodermus and others

Agaricus is genus that contains outstanding edible mushrooms, and many varieties exist in Arizona. Unfortunately, there are several sickening species in Agaricus, and some can be difficult to distinguish without performing a few key tests. Even worse, several great edibles share distinguishing properties with the sickening varieties.

The process of determining edibility in the genus Agaricus typically involves both a bruising color check and a scent test. The following two distinguishing properties must be noted in order to determine edibility:
- Yellow bruising / staining
- Phenolic vs. almond aroma

While each of these tests are very important in aquiring a proper ID, there are edible and sickening members that share similar test results. It is only in the collection of multiple traits that you will arrive at a satisfactory identification. Keep this in mind, and pay attention to your field guide!

Testing aroma:

To test for aroma, you will want to crush the edge of the cap with your fingers and smell for the release of aromatics. You will also want to do this with the stem (especially the base). Old specimens may have a much weaker aroma or none at all. Also, there are many Agaricus species that have a neutral "mushroom" aroma.

A phenol aroma, similar to the smell or ink or fresh asphalt, indicates the presence of a poisonous compound present in some Agaricus such as A. xanthodermus. Conversely, several highly prized edible Agaricus species exude an almond scent when their flesh is crushed. This is true of A. albolutescens and A. augustus, both excellent edibles that occur in Arizona.

Agaricus xanthodermus, a poisonous mushroom with a yellowing base and characteristic phenolic smell.
Photo: see stamp.

Testing bruising / staining:

To test for bruising, run a fingernail or a coin down the cap from the center to the edge. A more critical test is to slice the very base of the stem with a knife and watch for drastic color change. Some yellow staining reactions eventually turn brown. Many yellow staining Agaricus develop a yellow hue in age. The reaction is most prominent in slightly immature / recently matured specimens.

The most infamous of the poisonous Agaricus is Agaricus xanthodermus, the yellow staining meadow mushroom. This mushroom bears close resemblance to the popular edible meadow mushroom, but turns bright yellow when its cap is rubbed or the base of the stem is cut. You must note that yellow staining is not by itself an edibility criteria; there are yellow staining edible Agaricus out there. A. xanthodermus just has an especially strong staining reaction it is well known for.

The false morel
- Gyromitra spp.

Spring is the season for hunting morels. Few fungi produce mushrooms at this time of year. Unfortunately for morel hunters, one of these few is Gyromitra, the false morel. False morels appear in similar habitats and at similar times as regular morels, so it is important to be familiar with them.

The false morel contains a toxin called gyromitrin. It turns into a hydrazine compound in the body. Hydrazine is a dangerous compound used in jet fuels. You see where this is going...

The key differences between morels and false morels is are:

• True morels have a surface of pockets, looking a bit like a sponge.
• False morels look like tissue that has folded in upon itself.
• True morels have a hollow stem that runs from the base to the top of the mushroom.
• False morels have a solid stem that terminates where the cap begins. Any open spaces in false morels are irregular.

Tom Volk's website has an excellent article on Gyromitra. Another good article is posted at Morelmushrooming.com.

A good check to determine wether you have a true morel is to slice the mushroom in half. True morels have a hollow stem that is uninterrupted from top to bottom. False morels have solid stems and / or interrupted hollow cavities. Note the example here and see the difference.
Photos: mushroom-collecting.com

False morels: Gyromitra esculenta. Photo: Biopix.dk:JC Schou

A true morel. Note how there are true cavities in the surface.

The Green Gilled Parasol
- Chlorophyllum molybdites

The green gilled parasol mushroom thrives in urban habitats and can be found in large numbers when it appears. It most often occurs in the irrigated soils of lawns, golf greens, drainage areas, etc. C. molybdites primarily lives off of grass clippings, and often occurs in fairy rings.

The green gilled parasol is easy to identify because it is the only large classical mushroom to be found in the low desert. However, it closely resembles edible Agaricus such as the meadow mushroom. This is a big problem, as C. molybdites is poisonous. In fact, C. molybdites is the leading cause of mushroom poisoning in the Southwest.

Properties:
- Large, scaly, greenish-white cap
- Ring present on the stem, often loose and can be slid up / down
- Gills pale when immature but turn green as spores mature
- Found most often on irrigated, mowed lawns

It is very useful to become familiar with this common poisonous mushroom. It is probably the most frequently encountered of any entry on this page, considering its occurance in urban areas.

For a more detailed description, please visit the C. molybdites page at MushroomExpert.com.

P.S. Much to my suprise, I have found the green gilled parasol in lawns in Flagstaff, even at high elevation mixed conifer areas.