Dynamics of sporangium diffusion of Plasmopara viticola and its correlation with disease incidence in vineyard

Abstract：Airborne sporangium concentration of Plasmopara viticola is one of the key/actors ot grape downy mildew that has become more prevalent in Xinjiang. This study was initiated with the objective to gain a better understanding of the epidemiology based on relationships between airborne sporangium con- centrations and disease incidence in field. Environmental conditions, airborne sporangium concentrations of Plasmopara viticola, and severity of grape downy mildew were monitored for 3 years in field in Xinjiang. The results showed that predominant sporangia flew within the vineyard canopy. The daily dynamics of sporangium diffusion revealed dual-peak at 8：00 am and 8：00 pm, and higher at 8：00 pro. At P〈0.01 level, airborne sporangium concentrations were positively correlated with severity of grape downy mildew and air temperature, and negatively with humidity and rainfall in field. The sporangium initial diffusion of grape downy mildew was observed in early June, and its epidemic from June to September, and its daily peak were at 8：00 am and 8：00 pm in Shihezi of Xinjiang area. Airborne sporangium concentration of Plas- mopara viticola was a significant positive correlation with disease incidence in field.