Assessment Notes

Justification

Hygrophorus marzuolus is a rare, edible, ectomycorrhizal fungus mainly associated with Abies, Pinus and Fagus with an unusual fruiting period in late spring. The species is restricted to old forests. It is predominantly a European species distributed in temperate Europe around the Pyrenees, Alps and the Carpathians. Only isolated single and historical records are reported from bordering regions. It is nationally Red Listed in multiple European countries as threatened. Its population has decreased over the last 50 years due to a reduction of its potential habitat in old forest and probably also due to nitrogen deposition, and maybe collecting activities. Declines in area and quality of available habitat are thought to have exceeded 30% over the last 50 years (three generations); the decline in population size over this time could be higher. This decline in habitat is expected to continue over the next 50 years. Thus the species is assessed as Vulnerable A2cde+3cde+4cde.

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Taxonomic notes

The name has been used for both European and North American specimens. Based on difference in ecology, it is assumed that specimens from the two regions represent different species. This assessment is based only on European data. Further taxonomic research based on the comparison of DNA sequences is needed.

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Geographic range

Hygrophorus marzuolus is distributed in the temperate Europe around the Pyrenees, Alps and the Carpathians (Fraiture and Otto 2015, GBIF 2024). Few records come from bordering areas in Greece and North Macedonia, Russia (Caucasus, Krasnoyarsk, Tomsk), Pakistan and Morocco (Zervakis et al. 1998, Razaq and Shahzad 2005, Vaishlya et al. 2017). It is not known from Scandinavia and the United Kingdom. Most of the records (+300) come from Slovenia and Switzerland as a result of broad mapping projects.

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Population and Trends

The population of Hygrophorus marzuolus has decreased during the last 50 years due to reduction of its potential habitat of old forest, and probably also due to nitrogen deposition, and maybe collecting in some areas (C. Perini pers. comm.). It may be overlooked as it produce sporocarps in the spring outside of the main season. However, it is a well recognised and searched for species. The total population is estimated to be larger than 10,000 mature individuals.

The main host of H. marzuolus, Silver Fir (Abies alba) has showed a strong dieback in the 1980's in its range of occurrence in Europe (Tinner et al. 2013). Declines in area and quality of available habitat is considered to have exceeded 30% over the last 50 years (three generations; Dahlberg and Mueller 2011), and the decline in population size over this time could be higher. This decline in habitat is expected to continue over the next 50 years.

Population Trend: Decreasing

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Habitat and Ecology

Hygrophorus marzuolus mainly forms ectomycorrhiza with coniferous trees of the family Pinaceae, most often with Abies and Picea, but also with Pinus and Pseudotsuga (France). Rarely, it is found associated with Fagus sylvatica, Castanea sativa, Quercus cerris, Q. suber and Q. petraea. The fungus nearly exclusively occurs in natural or near-natural forests and only rarely in plantations. It has been recorded on calcareus as well as acidic and sandy soils. It produce sporocarps early in the spring, sometimes even under the snow in altitudes up to 2,000 m (Fraiture and Otto 2015).

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Threats

The population of Hygrophorus marzuolus is declining due to the loss of the suitable habitat, which is naturally grown old semi-natural or natural coniferous and mixed forests. Sites are mainly threatened by silvicultural intensification, but probably also due to nitrogen deposition, and maybe locally from over-collection (C. Perini pers. comm.).

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Conservation Actions

The species is Red Listed in most European countries where it is occurs; Austria (EN), Czechia (EN), Germany (EN), Hungary, North Macedonia (VU), Serbia, Slovakia (VU), and Switzerland (NT) (Kasom and Milickovic 2006, Fraiture and Otto 2015, Dämmrich et al. 2016, Dämon and Krisai-Greithuber 2017, Karadelev et al. 2022). It is protected by law in a few countries (Croatia, Germany, Serbia and Slovakia) and locally protected or picking is restricted in certain regions of Italy (Onofri 2005, Fraiture and Otto 2015).

Protection of sites is required where it grows with high conservation value, but selective cutting may be appropriate at sites of lower conservation values. Communities of ectomycorrhizal fungi, hence also Hygrophorus marzuolus, largely survive selective cutting as the majority of their host trees are left. Work to introduce some further active control of collection may also be beneficial (C. Perini pers. comm.). Desired research includes into its ecology, population biology and needed habitat conditions. Taxonomic research is needed to clarify the relationship between the European and North American taxon named the same, here considered being different taxa.

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Use and Trade

Hygrophorus marzuolus is an appreciated edible mushroom. In the past, it was sold on markets in Austria, France, Germany, Italy, and Switzerland (nowadays this is prohibited).

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Source and Citation

Kautmanova, I. 2025. Hygrophorus marzuolus. The IUCN Red List of Threatened Species 2025: e.T70406801A70406836. Accessed on 20 November 2025.

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• Country occurrence