Species of the genus Armillaria (Fr.:Fr.) Staude are widely distributed Basidiomycota belonging to the Agaricomycetes, and most are potential root-rot pathogens with a broad host range. Using interfertility tests, Korhonen (1978) separated European Armillaria within the annulate mellea complex into five biological groups later described as five biological species based on different ecological and physiological criteria. These species include Armillaria mellea (Vahl.:Fr.) Kummer, Armillaria ostoyae (Romagnesi) Herink, Armillaria gallica Marxmuller & Romagnesi, Armillaria borealis Marxmuller & Korhonen and Armillaria cepistipes Velenossky. In addition, two exannulate species include Armillaria ectypa (Fr.) Lamoure, found in peat bogs as a saprophyte, and Armillaria tabescens (Scop.:Fr) Emel, a forest species commonly found in southern Europe, usually considered as a saprotroph, but at least once reported in Europe as a weak parasite (Tsopelas & Tjamos, 1997). Armillaria mellea attacks vineyards, orchard trees and deciduous trees, but can also infect young conifers. Armillaria ostoyae is regarded as a parasite of coniferous trees, while A. gallica, A. borealis and A. cepistipes are all three generally considered as saprophytes (