بررسي بيماري سفيدك پودري درختان بلوط در جنگل هاي ارسباران

Introduction of the fungi causing powdery mildews on oak trees in Arasbaran forests.

Powdery mildews, are the most serious foliage diseases of oaks throughout the world with variable severity based on fungal agents involved and the host plants. Powdery mildews are more prevalent than any other diseases in Arasbaran forests and have extensively affected oak trees. Disease symptoms develops as occurrence of sporadic to uniform white cover spots on infected trees foliage. According to literatures, there are at least 15 fungal species as disease agents reported from 92 different oak species, of which, Erysiphe alphitoides var. alphitoides is the most important agent of powdery mildew on oak trees all over the world. In the course of this investigation after examining the samples collected from different oak trees of Arasbaran forests, 3 species of fungi causing powdery mildew, were isolated and diagnosed as the followings: 1) Erysiphe alphitoides var. alphitoides on oak species Qurecus macranthera, Q. petraea and Q. cf. komarovii. 2) Phyllactinia guttata on Q. petraea 3) Phyllactinia roboris on Q. macranthera and Q. petraea As sofar, there has not been any report of Erysiphe alphitoides on Q. cf. komarovii, Ph. guttata on Q. petraea and Ph. roboris on Q. macranthera, these 3 oak species are reported as Matrix nova for their related fungal agents respectively. Meanwhile, Ph. roboris is reported for the first time as a new species, for Iranian mycoflora.