INRA, Unit6 de Phytopharmacie et Mediateurs Chimiques, 78026 Versailles Cedex, France

Grey mould, caused by Botrytis cinerea, is one of the most damaging disease of grapevine. Today the main way to protect this crop consists in spraying fungicides between flowering and veraison. However, their utilisation is restricted because of resistance phenomena and difficulties in achieving maximum residue level values.
According to their mode of action the main botryticides can be classified into four groups [1]: fungicides affecting respiration: the oldest ones are multisite toxicants (e.g. dichlofluanid, thiram) whereas the most recent one fluazinam is an uncoupler. All of them are powerful inhibitors of spore germination and are not concerned by resistance. antimicrotubule toxicants: they are either benzimidazoles (e.g. carbendazim) or phenylcarbamates (e.g. diethofencarb). Negative cross-resistance occurs between these two families in the most common strains of B. cinerea. However, when the mixture carbendazim + diethofencarb is used intensively, double resistant strains are selected. dicarboximides and phenylpyrroles: dicarboximides (e.g. iprodione, procymidone, vinchlozolin) as well as the phenylpyrrole fludioxonil are highly active against grey mould. They induce similar morphological alterations of germ tubes (e.g. swelling, branching, bursting) and exhibit positive cross-resistance in laboratory mutants. Despite these similarities, the dicarboximide-resistant strains of B. cinerea found in vineyards remain sensitive to fludioxonil. anilinopyrimidines: cyprodinil, mepanipyrim, and pyrimethanil can block the excretion of hydrolytic enzymes (e.g. cellulases, proteases) and inhibit the biosynthesis of methionine. Anilinopyrimidine-resistant strains of B.cinerea has been detected in a limited number of French vineyards without reduced practical efficacy.

According to the evolution of fungicide resistance in B.cinerea and the introduction of new botryticides, the spray programmes against grey mould evolved continously [2]. For example, the present strategy in Champagne area consists in treating vineyards at the end of flowering, at bunch closing and at veraison with three different botryticides. More generally, the alternation of the various groups of botryticides with a maximum of one spray per year for each family has been adopted in all French vineyards.

1. Leroux P, 1995. Pesticide Outlook 6, 13-9.
2. Leroux P and Descotes A, 1997. Brighton Crop Protection Conference: Pests and Diseases, pp. 131-136.