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Oral: Pathogen Dispersal


Trapping conidia spores of Podosphaera aphanis in high tunnels and field strawberry plots.
R. ONOFRE (1), D. Gadoury (2), N. Dufault (1), N. Peres (1) (1) UNIVERSITY OF FLORIDA, U.S.A.; (2) Cornell University, U.S.A.

Strawberry Powdery Mildew (SPM) caused by Podosphaera aphanis can be severe on susceptible cultivars, especially in tunnel and glasshouse production. Epidemics of SPM are largely driven by intense sporulation and conidia dispersal, which are two highly relevant factors for management strategies. The objective of this study was to evaluate SPM aerial conidia spore concentrations in plastic tunnel and field environments of Florida. A 7-day recording volumetric spore trap was installed in both the field and high tunnel plots during the 2015-16 growing season. Airborne conidial dose at each site was recorded hourly for 5 weeks, as was temperature, relative humidity, leaf wetness and rainfall. In both plots, spore counts followed a diurnal pattern, with a peak in aerial concentrations between 10 am and 2 pm. Cumulative airborne dose in the tunnel (1488 spores/m3) was notably higher than in the field (82 spores/m3). Several coincident factors likely contribute to the airborne dose in tunnel growing systems, including an inherently more favorable environment for sporulation and infection, and subsequent increased disease severity. However, factors such as residence time of conidia within the system after becoming airborne, and effects of visible light and UV radiation on inoculum production and dispersal may also contribute to higher inoculum dose. Further work is being conducted to explore the effects of various environmental factors on conidia production and dispersal.