Ecological Factors Influencing Sporulation and Infection Cycles of Plasmopara viticola on Grapevine

Abstract

Ecological factors influencing sporulation and infection cycles of Plasmopara viticola on grapevine were investigated to understand the environmental drivers of downy mildew development. Field observations and controlled environment studies were conducted in grape-growing regions with recurrent disease incidence. Disease progression was monitored in relation to temperature, relative humidity, leaf wetness duration, and rainfall patterns. Results indicated that high humidity and prolonged leaf wetness were critical for successful sporulation and zoospore release, directly influencing infection initiation and secondary spread. Moderate temperature ranges were found to favor rapid pathogen development, while extreme temperatures inhibited sporulation efficiency and reduced infection success. Periodic rainfall events enhanced dispersal of sporangia and facilitated epidemic development under conducive microclimatic conditions. Infection cycles were strongly linked to canopy density and vineyard microclimate, where dense foliage created favorable humid niches for pathogen survival and multiplication. Temporal analysis revealed multiple infection cycles within a growing season, driven by alternating favorable and unfavorable environmental conditions. The study highlights the sensitivity of P. viticola to ecological variables and emphasizes the importance of weather-based disease forecasting. These findings provide valuable insights for optimizing fungicide scheduling and canopy management strategies to disrupt infection cycles and reduce downy mildew severity in grapevine production systems.