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Oral: Pathogen Dispersal


Validation of the CDM ipmPIPE Forecasting System: Relating Aerial Transport of Pathogen Spores to Outbreaks of Cucurbit Downy Mildew
K. NEUFELD (1), A. Keinath (2), B. Dutta (3), B. Gugino (4), D. Langston (5), M. Lewis Ivey (6), M. McGrath (7), S. Miller (8), E. Sikora (9), P. Ojiambo (1) (1) Department of Plant Pathology, North Carolina State University, U.S.A.; (2) Clemson Universit

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Cucurbit downy mildew (CDM) caused by Pseudoperonospora cubensis is considered the most damaging disease of cucurbitaceous crops worldwide. Sporangia produced by the pathogen are carried by wind currents and deposited on host plants following rain events. The CDM ipmPIPE forecasting system integrates data on current disease outbreaks and trajectories of sporangia transport from source fields to forecast the risk of new disease outbreaks in the eastern United States. The forecasting system was validated by relating the predicted risks of disease outbreak to the presence or absence of sporangia after a rain event and the onset of disease symptoms in the field. Rainwater samples from eight states, AL, GA, LA, NC, NY, OH, PA, and SC were collected from planting to the first report of disease during the 2013 to 2015 seasons. The presence of sporangia was then analyzed using primers specific to the pathogen. The pathogen was detected in 4-30% of the 203 samples collected from 2013 to 2015. Presence of sporangia in rainwater samples correctly classified disease onset in 67%, 81% and 78% of the cases, while the forecasting system correctly predicted disease onset in 75%, 85% and 60% of the cases in 2013, 2014 and 2015, respectively. Predictions from the forecasting system and presence of sporangia in rainwater samples were in agreement in 60-87% of the cases analyzed except in 2015 when presence of sporangia in rainwater samples were detected infrequently.