Model based humidity control of Botrytis in greenhouse cultivation

Botrytis cinerea is one of the most common plant pathogenic fungi that affects a wide range of greenhouse horticultural products and decreases their market value. B. cinerea can strongly decrease yield and post-harvest quality through latent infections. It is a highly water dependent fungus and a certain leaf wetness duration seems necessary for spore germination. However, during germination before building of the inocolum durations of dryness (desiccation) can kill the spores. To avoid grey mould disease incidence, the relative humidity set point is generally kept low. This costs high amounts of energy through dehumidification by heating and ventilating the greenhouses. Therefore, to control grey mould with climate control in a more specific way to save energy, a mathematical model simulating the microclimate in the greenhouse crop was used. The model calculates durations of leaf wetness and leaf dryness. The prediction of leaf wetness incidence is based on modelled leaf temperature at different locations in the crop and the dew point temperature. Duration of leaf wetness (i.e. time to dry out) is computed from the energy balance of latent heat on the leaf surface. Climate control is then optimised for energy saving and grey mould prevention. In the present paper, a simulation study was performed to test the performance of the model on greenhouse microclimate and energy saving. Simulations with a set of yearly reference climate data of Denmark showed high amounts of energy saving.