during visit beech forests of mazandaran province in may and june of 2010-2011, some infected twigs of fagus sylvatica with signs of fungal infection were collected. laboratory analysis revealed acervular fruiting bodies on infected twigs. acervulus up to 500 μm in diameter and forming a black spot on main and secondary twigs. conidia erumpent, form black masses over the acervulus. conidia are ...