The influence of climatic factors on downy mildew in two vineyards from France and Romania

Abstract

The objective of this study was to evaluate the influence of climate variability from the last two years, namely 2021-2022, on the development of the pathogen Plasmopara viticola in two vineyards renowned for the quality of their wines, Murfatlar (Romania) and Val de Loire (France). The study was carried out on four grapevine cultivars: 'Sauvignon blanc' and 'Cabernet sauvignon', authorized for the production of CDO Murfatlar wines; and Cot and Chenin, authorized for the production of CDO Touraine wines. The results regarding the appearance and development of the disease on leaves and bunches in different grapevine development stages, on the two variants of the experiments (treated and untreated) highlighted different levels of attack depending on the distribution of precipitation and the evolution of average air temperatures during the vegetation period. The excess rainfall regime in 2021 of 339.3 mm in Murfatlar and 351.8 mm in Val de Loire, and the air temperatures of 20-25°C generated optimal conditions for the spread of disease on the leaves in the untreated variant, reaching a maximum of 48.3% in Murfatlar and 9.5% in Val de Loire during veraison. The disease also spread to the bunches, reaching a maximum of 86.2% in Murfatlar, endangering almost completely the production of grapes. In the case of the variant where phytosanitary treatments were applied, the degree of attack was a maximum of 4%. In 2022, against the background of quantitatively reduced precipitation compared to 2021, with 64.15% in Murfatlar and 45.01% in Val de Loire, the first oil spots were identified in the untreated variant during BBCH 55 (the emergence of inflorescences), having an insignificant spread, reaching a maximum of 8.9% in the cluster compaction phenophase (BBCH 77).

Keywords

• plasmopara viticola
• air temperature
• rainfall
• degree of attack
• grapevine disease