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Ecology and Epidemiology

Spore Discharge by the Pecan Scab Pathogen, Cladosporium caryigenum. T. R. Gottwald, Research plant pathologist, USDA-ARS, Southeastern Fruit and Tree Nut Research Laboratory, Byron, GA 31008; Phytopathology 72:1193-1197. Accepted for publication 16 February 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1982.. DOI: 10.1094/Phyto-72-1193.

Conidial discharge by Cladosporium caryigenum from heavily diseased pecan leaf and nut shuck (involucre) tissue was studied under controlled exposure to relative humidity (RH), temperature, vegetative wetness (VW), and infrared radiation (IR). Spore release was minimal as RH decreased from near saturation to 40%, but further decrease stimulated considerable spore discharge which was enhanced by exposure to IR (>40 μE·m^–2·sec^–1). Sustained periods of constant RH <40% also favored spore release but were less favorable than RH that fluctuated above and below 40%. Spore release was stimulated by short (circa 1 min) IR exposures and brief (2-min) RH changes. Spore release was recorded only as the specimen dried off or when leaf wetness was maintained <15%. Vibration triggered spore release at low RH, especially when specimens were exposed to IR, but vibrational effects were considerably less effective than those reported previously for other hyphomycetes.