The strong taste of the fruit body may have some role in insects avoiding it. The small fly species "Megaselia pygmaeoides" feeds on and infests the fruit bodies of "T. felleus" in North America, though it seems to prefer other boletes in Europe. Fruit bodies can be parasitized by the mould "Sepedonium ampullosporum". Infection results in necrosis of the mushroom tissue, and a yellow colour caused by the formation of large amounts of pigmented aleurioconidia (single-celled conidia produced by extrusion from the conidiophores).