Efficiency of different strategies for the control of grey mold on grapes including gibberellic acid (Gibb3), leaf removal and/or botrycide treatments

Aim: The present work evaluated different strategies for the control of grey mold, caused by Botrytis cinerea, on wine grapes, including the use of the plant growth regulator Gibb3, leaf removal and/or botryticide treatments. The efficiency of the different control strategies (disease incidence and severity, yield) as well as the effect on the cluster structure was investigated.Methods and results: The trials were conducted in commercial vineyards in the Moselle Valley (Luxembourg) between the years 2007 and 2009, on the Pinot gris, Pinot blanc and Pinot noir grape varieties. The untreated control (T1) was compared to the following treatments : (T2) Gibb3, (T3) Gibb3 combined with leaf removal in the cluster zone after bloom, (T4) leaf removal after bloom combined with two times botryticides and (T5) Gibb3 combined with two times botryticides. The combination of Gibb3 with leaf removal or botryticide applications led to an efficiency level in grey mold reduction of around 60% and a decrease in cluster density when compared to the control. Moreover, we showed that the progression of grey mold disease was slowed down by the three treatments T3, T4 and T5.Conclusions: Gibberellic acid applied at full bloom as stand-alone treatment did not reduce in a significant way the compactness of the grape clusters and the impact on grey mold development was low. For a significant decrease of disease severity, gibberellic acid had to be combined with an additional measure, such as leaf removal or the use of botryticides. Based on its positive effect on cluster structure and microclimate, leaf removal can be recommended as a basic measure that can be further combined with an application of botryticides or gibberellic acid.Significance and impact of the study: All the tested strategies combining two measures have shown their potential to prolong the ripening period and therewith to improve wine quality. Moreover, the combined use of gibberellic acid and leaf removal represents a sustainable strategy for integrated viticulture due to its reduced input of organic-synthetic pesticides into the environment.

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