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Biological Characteristics of Elsinoë fawcetti Pertaining to the Epidemiology of Sour Orange Scab. J. O. Whiteside, Professor of Plant Pathology, University of Florida, Institute of Food and Agricultural Sciences, Agricultural Research and Education Center, Lake Alfred 33850; Phytopathology 65:1170-1177. Accepted for publication 16 May 1975. DOI: 10.1094/Phyto-65-1170.

Hyaline conidia of Elsinoë fawcetti required liquid water for their production, dispersal, survival, and germination, and a minimum wetting period of 2.5 to 3.5 hours to cause infection. Colored conidia, representing a morphologically distinct asexual spore form produced by this fungus, were liberated from conidiophores both by wind in excess of approximately 2 m/second and by water. Conidiophores that had previously borne colored conidia produced only hyaline conidia when wetted. Apparently, these conidiophores require some unknown environmental factor, in addition to high humidity, to produce colored conidia. When dispersed dry by wind, most colored conidia remained viable at least until the following night and then germinated with dew. Colored conidia dispersed by water in the daytime survived drying until the following night only if they remained attached to each other following detachment from the conidiophores. Because of the ability of colored conidia to survive postdispersal desiccation until dew was available for germination, some infection still ensued when the periods of canopy wetting by rain, overhead irrigation, or nonfungicidal sprays were too short to permit infection prior to drying.