Septoria chrysanthemella . [Descriptions of Fungi and Bacteria

Abstract

Abstract A description is provided for Septoria chrysanthemella . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Chrysanthemum indicum, C. japonicum, C. morifolium, C. parthenium . Also by inoculation on C. azaleanum, C. koreanum, C. leueanthemum, C. segetum, C. roseum, Tagetes patula, Centaurea cyanus (Punithalingam & Wheeler, 1965; Schneider, 1959). DISEASE: Formerly known as brown leaf spot or blight (Halsted, 1891; Cavara, 1892; Salmon, 1907; Moore, 1959) but now referred to as the black leaf spot of chrysanthemum (Hemmi & Nakamura 1927; Waddel & Weber, 1963) in order to distinguish the symptoms from those produced by Septoria obesa (CMI Descript. 139). The first visible leaf symptom is a small discrete necrotic spot. This gradually develops into a circular or elliptical spot seldom irregular, about 5-10 mm wide, at first dark brown, then turning black. Leaf spots of a purple to brown colour, with a distinct brown margin are not uncommon. The disease appears in susceptible chrysanthemum plants of all ages, first on the lower leaves and then gradually progressing upwards. This is a disfiguring disease and in a severe attack all leaves wither resulting in premature defoliation. GEOGRAPHICAL DISTRIBUTION: Africa (Ethiopia, Kenya, Malawi, Mauritius, Mozambique); Asia (China, Formosa, Japan, Pakistan, Philippines); Australasia (Australia, New Zealand); Europe (Austria, Azores, Bulgaria, Cyprus, Czechoslovakia, Denmark, France, Germany, Iceland, Italy, Norway, Portugal, Rumania, Spain, Yugoslavia, U.S.S.R.); North America (Canada, U.S.A.), Central America (Costa Rica, Cuba). (Literature; Herb. IMI). TRANSMISSION: Dimock & Allyn (24: 192) suggested the pathogen may survive the winter in the soil in infected debris from the previous season. The fungus may be disseminated by water splash or by mechanical means as with S. obesa .