Compared analysis of re-built long-term historical annual pressures of Botrytis Bunch Rot, Noble Rot and Downy Mildew in Bordeaux vineyards

International audience

anglais. The grapevine life history covers many decades, and the perennial crop is exposed year after year to several biotic hazards, including major harmful diseases, such as Botrytis bunch rot “BBR” (Botrytis cinerea) and downy mildew “DM” (Plasmopara viticola). B. cinerea is also known as the causal agent of the Noble rot “NR” process in maturing berries, resulting in highly prized, full-bodied sweet wines. Our aim was to reconstruct the grapevine past exposure to the two diseases and the NR process in the Bordeaux vine-growing region. The corresponding time series were analyzed based on specifically-designed annual prevalence/severity indicators.We used NR data from the Sauternes area, near Bordeaux, thanks to collaboration with Château d’Yquem. As for BBR and DM, we used advisory bulletins, provided to growers for almost one century by the French Agriculture Ministry. This information, from field disease monitorings by experts, was exploited by developing the following textual analysis (Fermaud et al, 2024, IOBC-WPRS Bulletin 171). First, for every disease and year, we extracted the keywords related to pathogen occurrence/prevalence within a given area, and its associated overall damage/severity. Second, by transforming these data into semi-quantitative scores and combining them, we designed an overall annual semi-quantitative score for every disease. The analyses of resulting databases from 1940 onwards, compared, for B. cinerea, the differences in vineyard expression and development according to the process considered, BBR vs NR. Furthermore, we compared the inter-annual dynamics patterns of the two major diseases BBR vs DM, by also investigating a possible interaction at this large temporal scale.In the current context of global warming and rapid changes in regulatory conditions, investigating and comparing such historical annual epidemic pressures may contribute to anticipate the necessary evolution(s) of grapevine protection and production systems, including also for such key pathogens, potential development of specific insurance policies.