Armillaria mellea
Confusion has surrounded the nomenclature and taxonomy of the species now known as "Armillaria gallica", paralleling that surrounding the genus "Armillaria". The type species, "Armillaria mellea", was until the 1970s believed to be a pleiomorphic species with a wide distribution, variable pathogenicity, and one of the broadest host ranges known for the fungi. In 1973, Veikko Hintikka reported a technique to distinguish between "Armillaria" species by growing them together as single spore isolates on petri dishes and observing changes in the morphology of the cultures. Using a similar technique, Kari Korhonen showed in 1978 that the European "Armillaria mellea" species complex could be separated into five reproductively isolated species, which he named "European Biological Species" (EBS) A through E. About the same time, the North American "A. mellea" was shown to be ten different species (North American Biological Species, or NABS I through X); NABS VII was demonstrated shortly after to be the same species as EBS E. Because several research groups had worked with this widely distributed species, it was assigned several different names.