[MoOmer]

I'm a member of the Illinois Mycological Association, where we do occasional surveys accompanied by biologists. They frequently take back tens of items for DNA sequencing.

If you're out there looking at a mushroom and think you know what it is, but aren't exactly 100% confident - remember that researchers who dedicate their academic career to fungi are frequently stymied by things found in a 2 hour walk with a few handfuls of volunteers: it might not be what you expect!

[pyinstallwoes]

How do they know if a mushroom is toxic?

[steelframe]

First, be cock-sure in your own ability to do something as simple and straightforward as identifying mushroom species because of your innate ability to recall every minutia of the field guides and your astonishing powers of perception and attention to detail. Then analyze closely the cap shape, scales, the gill/teeth/ridges/pore patterns in the cap underside including shape, width, spacing, depth, and color, the ridges, and the stalk, including a partial veil and/or annulus. Proclaim confidently when you have determined with 100% assurance that you know precisely what species of mushroom you have in your hand, because you are a mushroom genius.

At that point you can take a few bites. If you end up needing a liver transplant, then you know it was toxic.

[MoOmer]

Spore prints can be a huge help in identifying also!

There are some mushrooms that have very few known lookalikes (varies by geo/region), which have a handful of strong identifying factors. Morels, oysters, and a few others come to mind, where if you can confidently confirm these factors, you can be reasonably sure that you’ve identified them correctly.

That said, people sometimes convince themselves of these factors, especially when they haven’t had much experience identifying them before.

I do know a number of members of the IMA that have been there longer than me, and don’t forage at all!

[MoOmer]

I’m not an expert in the bio/chem side or really anything to do with mushrooms/fungi, but some families of mushrooms have commonly associated toxins. None of the below should be considered advice or recommendation or relied on in any way.

Amanitas often have a deadly toxin known as Amatoxin, for example.

Some others are sometimes reclassified from toxic to “sort-of-toxic” or “unknown.”

Common mushrooms like Morels can have their toxins cooked out (throw out the cooking water!), while others like Amatoxins will persist.

Still others affect some people, but not others - and some toxins induce negative effects in the presence of other chemicals in the system, like Inky Caps and Alcohol - the combination of which can be deadly, or not, depending on a number of factors.

My understanding of the situation overall is: it’s complicated.