1.1 Chemical control of grey mould in French vineyards The three major fungal pests of grapevine, powdery and downy mildew and grey mould aremostly controlled through the application of fungicides. Some of those are particularlyactive against the grey mould agent Botrytis cinerea. The panel of fungicides authorized inFrance comprise since many years anilinopyrimidines, benzimidazoles, dithiocarbamates,dicarboximides, phenylpyrroles and pyridinamines. Lately, the panel has been completed by fenhexamid, a sterol biosynthesis inhibitor (SBI) and the pyridine boscalid, a succinatedehydrogenase inhibitor (SDHI). In addition, a biofungicide based on the Bacillus subtilisstrain QST 713 (Serenade) has been authorized in 2010 against grey mould in vineyards. Thecompounds authorized against grey mould in French vineyards are listed in Table 1.Since grey mould may infect grapevine from flowering until harvest, optimal protectionneeds to be obtained during this period. Nowadays up to three treatments per season arerecommended in vineyards, corresponding to the stages A-C (A: flower cap falling – B:bunch closure – C: veraison). To reduce pesticide applications along with the general trendof reduction of chemical inputs in agriculture chemical treatments against grey mould arepositioned according to epidemiological and meteorological parameters. Grey mould notonly affects quantity of harvest but also the wine quality. Therefore, treatments also dependon the economic value of the wine. The number of treatments is variable between regionsand years according to the factors cited above.In those regions with regular applications of anti-Botrytis fungicides, especially in theNorthern regions, resistant strains have been selected which can ultimately lead totreatment failure. In order to reduce the risk of specific resistance development each antiBotrytis mode-of-action is limited to one application/season in France since the 90’s,involving alternations of different chemical families to combat grey mould in the vineyards.