Currently placed within the genus Butyriboletus (Wu et al., 2016). Was moved from the genus, Exudoporus (Vizzini, 2014), and before that from Boletus. There is a subspecies in Florida, Exudoporus frostii floridanus, sufficiently distinct as to be considered separately (Singer, 1947). It remains unclear whether the southern range of B. frostii is the subspecies floridanus, Nuhn et al. (2013) place the records from Costa Rica into this subspecies.
Butyriboletus frostii, commonly known as the “candy apple bolete”, is a mycorrhizal bolete fungus identifiable by its bright red cap and its tubes and pores, which take the place of gills. It is distributed across eastern North America, the southwest of the United States, Mexico, and various parts of Central America. B. frostii uses mainly oak as a substrate, and is threatened by the ongoing decline of oak populations in North America. Because this fungus is mycorrhizal, it is important for maintaining forest health. As such, as oak populations decline, B. frostii will suffer because of the loss of substrate, and the forest in turn will suffer from reduced mycorrhizae. This negative feedback loop means that factors which threaten B. frostii populations are likely intertwined with factors which threaten its forests. There is a need for greater research on B. frostii population size and trends, especially in the more isolated areas of its range (southwest of the United States and Central America).
Eastern North America, Southwest United States, Mexico, Central America (Kuo 2020) Aside from Costa Rica, distribution unknown elsewhere in Central America.
More research needed on population size and trends. Not considered rare, can be fairly common areas of range in eastern North America and Mexico. Status in Southwest and Central America more uncertain. Further work needed to understand taxonomy and relative distribution of subspecies. Slow decline of hardwood forests in some areas of range may correspond with similar declines in B. frostii.
Population Trend: Uncertain
Forms mycorrhizal associations with many hardwood trees, particularly oaks (Morris et al., 2009), but also pine (Vozzo, 1961) and Madrone in Mexico (Arora, 1986). It has been reported as common in moderately dense oak forests (Singer, 1947) and on sandy soils (Weber & Smith, 1980). Fruits between July and October, producing mushrooms either singly or in groups.
The species is threatened by the reduction of substrate available to it, namely oak (Bessette et al. 2017). The oak population of eastern North America is threatened by the impacts of climate change, invasive species, growing deer populations, and sociopolitical land disputes that disrupt adequate land management processes (Dey 2014). Note: species listed in the below IUCN classification threaten oak directly, B. frostii indirectly by harming its substrate. Some additional details about the classifications: 8.1.1 numerous introduced nonnative insect and plant species pose threats to oak populations in eastern North America; 8.1.2 Phytophthora ramorum, Limantria dispar, Agrilus planipennis; 8.2.2 Increase in white deer population, oak decline phenomenon (Dey 2014).
Preservation of old growth oak forests and regeneration of more novel oak populations will help bolster B. frostii by providing sufficient substrate for populations to grow. This will require a more scientifically and culturally informed land management approach, using controlled burns with infrequent, long inter-burn periods (as informed by Indigenous land management practices prior to the European colonization of the Americas) (Dey 2014). It will also be important to bolster efforts to identify, understand, and eradicate/manage invasive species that threaten oak populations, specifically Phytophthora ramorum, Limantria dispar, and Agrilus planipennis (Dey 2014). Limiting the soaring white deer population (Dey 2014) may also be an effective way to encourage the regrowth of natural oak forests — this may be an area where engaging hunters and hunting organizations with strict, ecologically-informed guidelines could be helpful. Finally, involving people involved in land management and conservation will be key to ensuring the success of any of these actions. There are plenty of publications outlining the threats to oak populations in the eastern North America; one possible way of raising more awareness of the plight of species dependent on these oaks (such as B. frostii), could be creating documentation that catalogues the organisms that are ecologically intertwined with oaks, to better classify the web of life that is under threat by oak decline. Private landowners control 58% of forested land in the United States (Oswalt et al. 2014), and conservation payments might encourage more landowners to invest in the often obscure and seemingly unprofitable practices required for oak regeneration.
More specific research on any direct threats to B. frostii populations would be a useful addition to the current body of research, as much is already known about indirect threats to B. frostii via reduction of its main substrate: oak. More research on the extent to which B. frostii is cultivated for human food might also aid in assessing the urgency of conservation efforts. Finally, more research is needed on B. frostii population size and trends, especially in the more isolated areas of its range (southwest of the United States and Central America).
B. frostii is an edible mushroom harvested by foragers. It is described as having a fruity taste (Alabama Mushroom Society, 2018).