The presence of four Armillaria species (Armillaria mellea, Armillaria gallica, Armillaria ostoyae and Armillaria tabescens) is reported for the first time in Greece. Compatibility tests as well as morphological studies of the mycelium in culture were used for species identification. Basidiocarps were produced in vitro by all four species, however their ability to fructify differed significantly among them. Armillaria ostoyae was recorded on coniferous and mixed forests causing considerable damage. This fungus was found in northern Greece only, where it seems to be the southern limits of Armillaria ostoyae in the Balkans. Armillaria mellea and Armillaria gallica were common on coniferous and broadleaved forests throughout Greece. Armillaria gallica was found to infect fir trees suppressed in the understory or trees weakened by some other factor. This species was present as a saprophyte on the beech forests of central and northern Greece. On the other hand, Armillaria mellea appeared to be a primary pathogen, killing trees of all ages on fir and aleppo pine forests. Finally Armillaria tabescens was recorded in a few cases, on almond tree orchards in central Greece.
