Septoria humuli. [Descriptions of Fungi and Bacteria].
Abstract A description is provided for Septoria humuli. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOST: Humulus lupulus (hop). DISEASE: Leaf spot of hop leading to premature defoliation. The disease has been reported initially to be confined to older and lower leaves and subsequently spreading to younger and upper leaves (Putto, Koul & Saraf, 1975). Female plants have been reported as being more susceptible than male plants. The visible symptoms are minute circular or irregular lesions, 1-3 mm wide and prominent on both surfaces of the leaves. With the progress of infection these lesions enlarge to form well defined spots, up to 6 mm wide, with ash white centres. Occasionally spots coalesce to form leaf blotches. Often severely infected leaves are killed and one report claims leaves on vines up to a height of 2-3 m have been affected (5, 1985). GEOGRAPHICAL DISTRIBUTION: Asia (India, Himachal Padesh, Kashmir); Europe (Czechoslovakia, Belgium, France, Germany, Hungary, USSR); North America (USA, Kansas, New Hampshire). TRANSMISSION: No specific studies reported. Presumably by conidia disseminated by water splash during hot weather.