Tricholoma equestre

Tricholoma equestre or Tricholoma flavovirens, also known as Man on horseback or Yellow knight is a formerly widely eaten but hazardous fungus of the Tricholoma genus that forms ectomycorrhiza with pine trees.

Known as Grünling Pilz in German and canari in French, it has been treasured as an edible mushroom worldwide and is especially abundant in France. Although it is regarded as quite tasty, cases of poisoning from eating T. equestre have been reported. Research has revealed it to have poisonous properties.

Description
The stem is yellow, usually about 4 to 10 centimetres long with an even diameter. The gills are also yellow colour and the spores are white. The hat is usually a yellow to yellow-green sometimes with a touch of brown to brown-reddish colour. The diameter is usually from 5 to 12 centimetres in length. The skin layer covering the hat is sticky and can be peeled off.

It can easily be mistaken for a variety of other members of the Tricholoma genus, such as T. auratum, T. aestuans and T. sulphureum.

Classification
Tricholoma equestre was first described as Agaricus equestre by Linnaeus in 1753, predating a description of Agaricus flavovirens by Persoon in 1793. Thus this specific name meaning "of or pertaining to horses" in Latin takes precendence over Tricholoma flavovirens, the other scientific name by which this mushroom has been known.

The species may be in need of further analysis given the conflicting reports of toxicity.

Toxicity
Long regarded as one of the tastier edible species, concern was first raised in southwestern France. People who have been poisoned have all had three or more meals containing T. equestre within the last two weeks prior to treatment. One to four days after their last meal containing the fungus, the patients reported weakness of the muscles, sometimes accompanied by pain. This weakness progressed for another three to four days accompanied by a feeling of stiffness and darkening of the urine. Periods of nausea, sweating, reddening of the face were also registered, but there were no fevers.

The still unknown poison in T. equestre accumulates in the muscles and can lead to Rhabdomyolysis.

As yet, there have been no reported cases of poisoning in North America, and there is speculation that the respective mushrooms may in fact be different species that are very similar in appearance.

There are reports where patients treated for T. equestre poisoning have died, likely as a result of the poisoning.