Improved leaf pruning reduces development of stem cankers caused by grey mould in greenhouse tomatoes

Botrytis cinerea, the causal agent of grey mould, is considered as a major burden on greenhouse tomato production. In heated greenhouses, where leaf pruning is a routine practice and microclimatic conditions are favourable for grey mould development, infections of the pruning wounds result in stem cankers that can rapidly kill the plants. Chemical control is not always sufficiently effective and growers face increasing demands for reducing their dependency on pesticides. Several techniques can be used for the removal of leaves. They differ mainly on the presence or absence and the size of petiole stubs remaining on the stems after pruning. In this study, leaf pruning techniques were compared in an experimental greenhouse and the results validated in four commercial greenhouses, in a variety of agronomic conditions and in various situations of inoculum pressure. All experiments clearly showed that a careful removal of the leaves without leaving any petiole stubs on the stems can significantly decrease the incidence of stem cankers even under high disease pressure. As up to 10-fold differences were observed, this suggests the possibility of improving pruning practices in tomato greenhouses by removing leaves systematically close to the stem. This environmentally-friendly cultural practice appears compatible for integration with other preventative methods for the objective of sustainable crop protection in greenhouse tomatoes.