Royal bolete

Butyriboletus regius


Кралски вргањ



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Assessment info
Habitat and Ecology
Use and Trade
Conservation Actions


Scientific name

Butyriboletus regius


(Krombh.) D. Arora & J.L. Frank


Boletus regius (Krombholz) D. Arora & J.L. Frank

Suillus regius (Krombh.) Kuntze

Assessment info

IUCN Red List Category and Criteria

Vulnerable C2a(i)

Date assessed

November 2020


Tofilovska, S.


Kost, G.

Mešić, A.


Karadelev, M.

Rusevska, K.

Gjorgonoski, M.


Miskovic, M.


Butyriboletus regius is found in deciduous forests, on wet slopes, where it forms ectomycorrhiza mainly with Quercus, and it is less frequently reported from Fagus and Castanea forests in our country. It has been registered at 70 sites, broadly dispersed in 30 biogeographic regions; however, at the observed sites it has been reported as extremely rare, just a few individuals per subpopulation. The total number of sites is guesstimated to be up to 140 sites, and an estimate can be made of ca. 2,800 mature individuals. An ongoing decline in population size is due to deforestation leading to loss of habitat area and diminished habitat quality. The species is therefore assessed as Vulnerable under C2a(i) criterion.


Current population trend



Butyriboletus regius is reported as extremely rare at the observed sites, one observation per site. According to the instructions for estimation of mature individuals provided by Dahlberg and Mueller (2011), an estimate can be made of ca. 2,800 based on the probable total number of sites in the country (ca. 140), the estimated number of functional individuals at each locality (estimated to be two), and the template of how many mature individuals each reproducing genotype may give rise to (the template used ten). An ongoing decline in population size is due to deforestation leading to diminished habitat quality.

Habitat and Ecology


1 Forest
1.4 Forest – Temperate

Habitat and Ecology

Butyriboletus regius occurs in deciduous forests, and it forms ectomycorrhiza principally with Quercus, and it is less frequently reported from Fagus and Castanea forests in our country. Suitable environment is old, sunny, semi-open forests, on wet slopes, with preference for calcareous soils. The species usually produces sporocarps from mid-spring to mid-autumn, infrequently and in a small number while in rainy summers it is documented as more common, producing a higher number of sporocarps.
It has been recorded at 70 sites in the country, broadly dispersed in 30 biogeographic regions (Melovski et al. 2013), at elevation ranges between 400 and 1,600 m. Only one of the known sites is located in a national park, in Galicica NP, in the zone for sustainable use. The species is edible, conspicuous, so it has been searched for in the past, and it has been reported. Nonetheless, since it grows in broadleaf forests, which are the dominant forest cover in the country, an estimation of probable sites has been made (Dahlberg and Mueller 2011). The total number of sites is guesstimated to be twice as high as the current number, thus it is ca. 140 sites.

Use and trade

Use and trade

It is an edible species, highly appreciated among the edible boletes. It is collected by mushroom foragers, but it is not traded by mushroom purveyors where Boletus edulis Bull., Boletus aereus Bull. and Boletus pinophilus Pilát & Dermek are chiefly sold.



The species is generally threatened by continuous loss and fragmentation of oak as well as beech forests attributable to logging activities while sweet chestnut forests occupy a minor area, ca. 4,000 ha in the entire country.

In line with available statistics data and publications, 91% of the total forest covered area in North Macedonia is managed, and most of it (93%) is regarded as productive forest whereas the remaining area is also managed only with a restriction in regard to the logging system (Trajkov et al. 2016, Kolevska et al. 2017). In practice, the silvicultural system has clear-cutting in oak forests and at places of beech forests too; as a result bare lands and even-aged forests are created while old growth forests are in decline (Trajkov et al. 2016). Annually ca. 1% of forests are logged (Kolevska et al. 2017, State Statistics Office 2018), and illegal logging is considerably high, with additional 30% to legal wood extraction.

Therefore, the total number and quality of suitable habitats is continuously dropping, posing a major threat to maintenance of a stable population.

Decline in health of forest stands due to diseases on Quercus spp., Fagus sylvatica and Castanea sativa with varying degrees of intensity have been reported (DPRS 2019). Diseases of oak stands are primarily caused by Euproctis chrysorrhoea L., Lymantria dispar L. and species of the family Tortricidae, of beech trees by Rhynchaenus fagi L. while diseases of sweet chestnut trees by Cryphonectria parasitica (Murrill) Barr. (DPRS 2019).

Another threat is excessive foraging of this edible species. Habitat damage may be irreversible if a single site is excessively and repeatedly harvested. Intensive clearing up of leaf litter and soil along with soil trampling and erosion damage the mycelia and change the microhabitat.

In the future, long periods of drought will have a negative impact on maintenance of the population and its area of distribution as unfavourable conditions for fructification of the fungus.

Conservation actions

Conservation actions

Conservation needed: The already known sites must be protected against utilisation of the ectomycorrhizal partner, and they should be preserved in their natural condition. Due to the type of silvicultural management of oak forest (Trajkov et al. 2016), in order to maintain a good habitat quality, it is vital to constitute forest reserves with maintenance of semi-open conditions at certain places and practice oak recruitment. At places of logging activities, instead of clear-cutting, trees of various age should be left on site. Reforestation in the lower oak belt with alien tree species rather than oak should not be applied.

Research needed: Regular monitoring on an annual basis at the established sites, coupled with field research at potential sites in order to explore the distribution and dynamic of occurrence of Butyriboletus regius. Assessment of forest health and, if required, undertaking essential measures to preserve the health of forest stands. It is advisable to digitize and regularly update forest inventories and forestry plans. There is a necessity of elaboration of a habitat map.



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