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Ecology and Epidemiology

Patterns of Diurnal and Seasonal Airborne Spore Concentrations of Fusicladium effusum and its Impact on a Pecan Scab Epidemic. T. R. Gottwald, Research plant pathologist, Southeastern Fruit and Tree Nut Research Laboratory, Byron, GA 31008; P. F. Bertrand, extension plant pathologist, University of Georgia, Rural Development Center, P. O. Box 1209, Tifton, GA 31793. Phytopathology 72:330-335. Accepted for publication 10 August 1981. 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-72-330.

Aerial concentrations of conidia of Fusicladium effusum, the causal organism of pecan scab, were monitored in 1980 with a Burkard 7-day recording spore trap to measure dispersal by air. Dispersal by rainwater was measured with funnel traps each with sporulating scab lesions on nut shucks, twigs, and leaf petioles held between screens above the funnel. Rainfall reduced hourly air spore catches. Aerial concentration of conidia was reduced by prolonged periods of drought. Aerial dispersal accounted for most of inoculum recorded. Aerial spore concentration peaked at midday and usually exhibited diurnal periodicity. Appreciable conidia dispersal started in late April and continued through November with maximum air spore concentrations occurring between June and October. Maximum air spore concentration coincided with decreasing periods of vegetative wetness and decreasing relative humidity during drying periods following dew or rainfall.

Additional keywords: epidemiology, spore dispersal, inoculation, Cladosporium.