Modelling Botrytis cinerea spore exchanges and production in unheated greenhouses

Abstract : In order to devise optimal and sustainable strategies to protect greenhouse grown crops against Botrytis cinerea, production of spores inside the greenhouses and exchanges with the outside need to be monitored. Such knowledge could be used for adequate timing of measures aimed at limiting the entry of exogenous inoculum and others aimed at limiting the multiplication of the endogenous inoculum. In an earlier study, a model based on spore mass balance was developed to estimate the production of B. cinerea spores inside a greenhouse and the number of spores entering and leaving the greenhouse. This model was successfully used in a heated glasshouse. As much of the tomato production also occurs in more open and less controlled conditions, the present study aimed at testing the model in non heated plastic greenhouses (tunnels) where environmental parameters known to influence spore exchanges and production differ from a glasshouse setting. When diseased plants were present in the tunnel, the production of spores over 24 h estimated by the model was equivalent to 5 to 10% of the maximum potential amount present on the plants, which was coherent with the amount of spores likely to be released by the action of wind on sporulating lesions. Exchange of spores was toward the outside. When the tunnel was empty or contained disease-free plants, fewer spores were exchanged and the spore movement was globally from the outside toward the inside of the tunnel.