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Factors Affecting Dispersal of Conidia of the Apple Scab Fungus. T. B. Sutton, Research Associate, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824, Present address of senior author: Department of Plant Pathology, North Carolina State University, Raleigh 27607; A. L. Jones(2), and L. A. Nelson(3). (2)Associate Professor, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; (3)Professor, Department of Statistics, North Carolina State University, Raleigh 27607. Phytopathology 66:1313-1317. Accepted for publication 30 April 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1313.

Dispersal of conidia of Spilocea pomi, the imperfect stage of Venturia inaequalis, was monitored in air during the summers of 1973 and 1974 with a Burkard recording volumetric spore trap and in rainwater during 1974 using funnel traps. Rain was an important mechanism for disseminating conidia; however, significant numbers of conidia also were detected in air. Aerial dissemination was diurnal with peak conidium frequency occurring between 1400 and 1600 hours Eastern Standard Time (EST) and with a subsidiary peak around 2100 to 2200 hours EST. Correlation and multiple regression analyses were used to relate counts of trapped conidia to several meterological factors and to determine their relative importance in the release of conidia. Trap counts of conidia were not related to any dominant environmental parameter, but to the interaction of several. Release of conidia was positively correlated with temperature, wind velocity, and solar radiation, but negatively correlated with leaf wetness and relative humidity. Analysis of disease progress data in relation to availability of conidia and to infection periods suggests that airborne conidia contribute to disease increase, particularly during dry periods.

Additional keywords: epidemiology.