During April 2013, branches of oak (Quercus brantii Lindl.) with fungal infection were collected from Kohkiluyeh and Buyer Ahmad province of Iran. Laboratory survey indicated acervuli on the samples of oak dead twigs (3mm diameter). Acervuli immersed in bark, were scattered, small (500µm), flat to subconical, 3-4 angled gray to black, hymenium labyrinthiform, pale grey, finally smeared over with golden yellow startum of spores. Conidiophores were crowded, branched, acicular, nearly straight, about as long as the conidia. Spores abundant, slender, and strongly arcuate, 20-42 (35/6) × 0/6-0/8 (0/7) µm. According to Barnett and Hunter (1998) and Grove (1937), this fungus was identified as Libertella quercina Tul. Saccardo (1906) described Cytosporina quercina (Tul.) Traverso (basionym: Libertella quercina) on branches of Quercus and Castanea in Italy, France, and Germany. It is the anamorphic state of Diatrypella quercina (Pers.) Cooke. Teleomorphic state was not found on our samples. This is the first report of Libertella quercina for mycobiota of Iran.
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