Slippery jack

Suillus americanus


Моликово волчјо лепче



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Not evaluated Data deficient Least concern Near threatened VULNERABLE Endangered Critically endangered Extinct in the wild Extinct
Assessment info
Habitat and Ecology
Use and Trade
Conservation Actions


Scientific name

Suillus americanus


(Peck) Snell


syn. Suillus americanus f. helveticus (Singer) Klofac

syn. Suillus sibiricus (Singer) Singer

syn. Suillus sibiricus subsp. helveticus Singer

Assessment info

IUCN Red List Category and Criteria

VU – Vulnerable D1

Date assessed

November 2020


Tofilovska, S.


Kost, G.


Karadelev, M.

Rusevska, K.

Jovanovski, T.


Miskovic, M.


Suillus americanus is forming an ectomycorrhizal symbiosis with five-needle pines. In our county it is a rare species registered only at five sites and is mainly dependent on the mycorrhizal partner Pinus peuce, a Tertiary relict, which is not widespread in the country. Given the knowledge on availability of appropriate habitat and the ecology of the species the estimated number of locations is not expected to be higher than 10. Based on the currently known and predicted sites, the estimate of population size is ca. 300 mature individuals. The species is assessed as vulnerable under criteria D1.


Current population trend



The species is present on a small number of sites, with the highest occurrence at Pelister NP. According to the instructions for estimation of mature individuals provided by Dahlberg and Mueller (2011), based on the currently known and predicted sites, the estimate is ca. 300 mature individuals (10 total numbers of sites x 3 functional individuals at each locality x 10 mature individuals each functional individual may give rise to). Given the state of the appropriate habitat, the population trend is stable.

Habitat and Ecology



Habitat and Ecology

Suillus americanus mainly occurs in the mountain and subalpine zone, forming an ectomycorrhizal symbiosis with five-needle pines. In Europe, it is associated with Pinus cembra and P. peuce; in North America with P. monticola, P. flexilisand P. strobes; in Siberia with P. pumila and P. sibirica whereas in Asia with P. wallichiana. Even though in most of literature it is allied to five-needle pines exclusively, in Pakistan a mycorrhiza with roots of Abies pindrow, Salix alba and Populus sp. has been described (Sarwar et al. 2011, Sarwarand Khalid 2014), and in India Cedrus deodara and Picea smithiana are mentioned (Verma and Reddy 2016). It grows solitary to scattered and gregarious on both calcareous and siliceous bedrock, registered from acid to neutral and basic soils, with low to moderate nitrogen content (Favre 1960, Fraiture and Otto 2015, Verma and Reddy 2016).

In North Macedonia it is mostly found in old-growth Pinus peuce forests, at an altitude ranging between 1,400-1,800 m a.s.l. from early summer till late autumn (Karadelev and Rusevska 2008, Karadelev et al. 2018) in mountains Pelister and Kajmakcalan. It has only one locality in forest stand of planted Pinus strobus at 900 m a.s.l. in mountain Kitka. Other potential localities are the forests of Macedonian pine in Shar Mountain, in the vicinity of Leshnica and Jelachki Crn Vrv (UNEP 2020). The mycorrhizal partner can be found in other localities too, but those forest stands are recently established (Mandzukovski et al. 2009). Therefore, given the knowledge on availability of appropriate habitat the estimated number of locations is not expected to be higher than 10.

Use and trade

Use and trade

Suillus americanus is reported as edible but it lacks any commercial or high culinary value.



Notwithstanding the fact that the species has a broad distribution and it might be common in certain countries, at the national level it might be under threat, as already recognised in the above-mentioned European countries.

The biggest population is in Pelister NP in the Strict Protection Zone and part in the Sustainable Use Zone where there is no direct threat to the species. The natural succession of Macedonian pine by fir and beech forest is already recognized (Acevski and Simovski 2009), so the newly established forest stands are necessary for maintaining the population. Nevertheless, a small but continuous increase in area under Macedonian Pine is noted in the last ten years, according to the data provided by State Statistical Office (2018).

Logging activities, potential loss of habitats by construction of sky-runs and other infrastructure in the subalpine region pose a risk to the species in the unprotected areas.

Plant pathogen fungus and three bark beetle species recognized as pests, have been identified in Macedonian Pine forest causing drying out of the wood, specifically, Ips sexdentatus Börner, Ips typographus Linnaeus and Ips amitinus Linnaeus. Yet, this pathogen fungus and beetle pests do not pose a threat to the survival of Macedonian Pine, and consequently, to Suillus americanus but the status needs to be monitored closely (DPRS 2019).

Additionally, the threat by air pollution due to nitrogen deposition is real given that even in protected areas, the immense and persistent overburdening of nutrients through air occurs (Paoletti et al. 2007).

Conservation actions

Conservation actions

Conservation needed: The survival of this fungus depends on the health of its habitat and the ectomycorrhizal partner. Hence, preservation of Macedonian pine is imperative at all sites. The site on Kajmakcalan should be maintained in its natural condition and logging should be forbidden in order to sustain the genetic diversity of the fungus in the country. Conservation of other possible sites suitable for growth of this fungus should also be taken into consideration, such as the Macedonian pine in Shar Mountain. Furthermore, at all sites, the habitat condition, in particular the health of the mycorrhizal partner, infections by pests and plant diseases must be regularly followed during the year, and if necessary appropriate prevention and control methods should be applied to preserve the health of the forest stands. Forestation with alien species should not be conducted.

Research needed: Regular monitoring on an annual basis at the established sites, coupled with field research at the potential sites and the recently established forest stands noted by Mandzukovski et al. (2009), in order to explore the distribution and dynamic of occurrence of the species. It is advisable to digitize and regularly update forest inventories and forestry plans. There is a necessity of elaboration of a habitat map.



Acevski, J. and Simovski, B. 2009. Successive processes in old Macedonian Pine forest at locality “Begova Ceshma” in the national park “Pelister”. Forest review 42: 140-146.

Dahlberg, A. and Mueller, G.M. 2011. Applying IUCN red-listing criteria for assessing and reporting on the conservation status of fungal species. Fungal Ecology 4(2): 147-162. doi:10.1016/j.funeco.2010.11.001

Diagnostic Prognostic Reporting Service of Republic of Macedonia (DPRS). 2019. Report on the state of plant diseases and pests in natural and newly established forest plantations in the Republic of Macedonia. Ministry of Agriculture, Forestry and Water Economy – Sector for Forestry, pp. 89, Skopje.

Favre, J. 1960. Catalogue descriptif des champignons supérieurs de la zone subalpine du Parc National Suisse. Résultats rech. scient. entreprises Parc Nat. Suisse VI (N.F.) (42): 323–610.

Fraiture, A., and Otto, P. 2015. Distribution, ecology and status of 51 macromycetes in Europe. Results of the ECCF Mapping Programme. Meise, Botanic Garden Meise.

Friebes, G., Dämon, W., Michelitsch S., Pidlich-Aigner H. and Krisai-Greilhuber, I. 2017. Verzeichnis und Rote Liste der Großpilze der Steiermark (Österreich). Joannea Botanik 14: 29–112.

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Index Fungorum Partnership. 2020. Index Fungorum. Royal Botanic Gardens Kew and Chinese Academy of Science (the custodians).  Available at:

Karadelev, M. and Rusevska, K. 2008. Bern convention fungi candidates from Macedonia – I. (Boletus dupainiiPhylloporus rhodoxanthus and Suillus sibiricus ssp. helveticus). Biologia Macedonia 61: 7-14. ISSN: 1857-5277.

Karadelev, M., Rusevska, K., Kost, G. and Mitic-Kopanja, M. L. 2018. Checklist of Macrofungal Species From the Phylum Basidiomycota of the Republic of Macedonia. Acta Musei Macedonici Scientiarum Naturalium 21(1): 23-112.

Kasom, G. and Miličković, N. 2006. Protected species of macromycetes in the Republic of Montenegro. Institute for the Protection of Nature, Podgorica, Montenegro.

Lizon, P. and members of the Slovak Mycological Society. 2001. Red List of Slovak Fungi – draft. Bratislava, Slovakia.

Mandzukovski, D., Acevski, J. and Jovanov T. 2009. Extension of the areal of Macedonian Pine (Pinus peuce Grisb.) in the R. of Macedonia. Forest review 42: 155-162.

Nguyen, N., Vellinga, E.C., Bruns, T.D. and Kennedy, P. 2017. Phylogenetic assessment of global Suillus ITS sequences supports morphologically defined species and reveals synonymous and undescribed taxa. Mycologia 108(6): 1216–1228. DOI: 10.3852/16-106.

Paoletti, E., Bytnerowicz, A., Andersen, C., Augustaitis, A., Ferretti, M., Grulke, N., Günthardt-Goerg, M.S., Innes, J., Johnson, D., Karnosky , D., Luangjame, J., Matyssek, R., McNulty, S., Müller-Starck, G., Musselman, R. and Percy, K. 2007. Impacts of air pollution and climate change on forest ecosystems — emerging research needs. The Scientific World Journal 7(Suppl. 1): 1-8. DOI 10.1100/tsw.2007.52.

Peev, D., Petrova, A.S., Anchev, M., Temniskova, D., Denchev, C.M., Ganeva, A., Gussev, C. and Vladimirov, V. (eds). 2015. Red Data Book of the Republic of Bulgaria. Vol. 1. Plants and Fungi. Sofia.

Sarwar, S., Hanif, M., Khalid, A.N. and Guinberteau, J. 2011. Diversity of Boletes in Pakistan – focus on Suillus brevipes and Suillus sibiricus. Proceedings of the 7th International Conference on Mushroom Biology and Mushroom Products.

Sarwar, S., Khalid, A.N. 2014. Diversity and Phylogeny of Suillus (Suillaceae; Boletales; Basidiomycota) from coniferous forests of Pakistan. International Journal of Agriculture and Biology 16: 489–497.

Senn-Irlet, B., Bieri, G. and Egli, S. 2007. Rote Liste der gefahrdeten Grosspilze der Schweiz. BAFU, WSL, pp. 92, Bern.

State Statistical Office. 2018. MakStat database. Available at: (Accessed: 13 March 2020).

UNEP Regional Office in Vienna. 2020. Study for valorization of Shar Mountain. Tetovo-Skopje, pp. 683.

Verma, B. and Reddy, M.S. 2016. Diversity of the genus Suillus Gray from coniferous forests of the northwestern Himalayas, India: Taxonomy, ecology and some new records. Kavaka 47: 114 -124.

Wojewoda, W. and Ławrynowicz, M. 2006. Red list of macrofungi in Poland. Kraków Available at: