Effects of Rain‐shelter Cultivation on the Temporal Dynamics of Grape Downy Mildew Epidemics

Grape downy mildew (GDM), which is caused by Plasmopara viticola (Berk et Curt.) Burl. & de Toni, is the most destructive grapevine disease in the world. In this study, we chose three cultivars that differ in their resistance to GDM and compared the effects of rain‐shelter cultivation and open‐field cultivation methods on GDM epidemics (2012–2015). The temporal dynamics of GDM were examined over a 4‐year period the results indicated that the disease index fit an S‐shaped curve, and further analysis revealed that a logistic model best fit the disease development and derived epidemic periods. Rain‐shelter cultivation significantly delayed the epidemic onset by 30 days, reduced the epidemic phase by 4 days, and decreased the final disease index by 50% as compared to open‐field cultivation. The logistic and decline phases were shortened significantly by 7 and 21 days under rain‐shelter conditions, respectively. Moreover, the rain‐shelter cultivation technique effectively decreased the highest apparent infection rate and standard area under the disease progression curve values associated with reduced disease severity. The above results demonstrate that rain‐shelter cultivation significantly affects temporal dynamics parameters of GDM. Meteorological factors had significant effects on the GDM epidemic in that the apparent infection rate was significantly positively correlated with mean temperature, relative humidity, rainfall, and leaf wetness duration before the first week of the experiment.