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Contested ecology, growing gregariously. Fruiting summer through fall. Widely distributed in Eastern North America. Cap 5-20 cm wide, irregular cap, wavy margins, ochre to reddish-brown, tacky when wet and leathery when dry. Pores yellow, irregularly shaped with cross-veins, staining slowly blue then reddening over time. Stem 2-4 cm, off-center, same color as cap. Boletinellus merulioides is known for forming plentiful sclerotia in the Eastern region of North America (Cotter and Miller 1985). When germinated, the sclerotia collected in the forest formed mycelial colonies that had the same characteristics as colonies formed from sporocarps (Cotter and Miller 1985). This fungus was historically presumed to be ectomycorrhizal, however its primary host tree, Fraxinus americana, forms vesicular-arbuscular mycorrhizal connections, which was assumed to preclude ectomycorrhizal relationships (Nuhn 2016). Research from 1987 suggested a mutualistic relationship with the aphid Prociphilus fraxinifolii (Brundrett and Kendrick 1987); recent isotopic field analysis confirmed ECM relationships between B. merulioides and F. americana, but could not rule out honeydew from P. fraxinifolii as a potential carbon source (Nuhn 2016). ID number: 05.60.01.2022
White, Kathleen R.; Jergensen, Jacqueline A.; and Lam, Ada, "Boletinellus merulioides" (2022). Mycological Herbarium of Macrofungi from the East Brook Valley. 22.