Estimation of greenhouse tomato infection risk by Botrytis cinerea based on temperature and relative humidity

In recent years, data loggers and sensors that continuously measure temperature and relative humidity have been widely used in protected horticulture. This study evaluates a method for estimating the infection risk of greenhouse tomatoes by Botrytis cinerea using temperature and relative humidity. In June 2018, the temperature and relative humidity in the tomato cultivation greenhouse were recorded at 10-min intervals. The petals attached to young fruit were inoculated with conidia of B. cinerea at intervals of 2 to 3 days, and the occurrence of gray mold in inoculated petals was observed over time. The cumulative time of effective infection over the previous 2 days was calculated based on temperature, relative humidity, and adjustment factors by mycelial growth temperature. As a result, the disease incidence was in good agreement with the increase/decrease in the cumulative time of effective infection. Therefore, an index was designed to evaluate the risk of infection on a three-point scale (safety, caution, and dangerous) based on the cumulative time of effective infection. Upon investigating the relationship between the disease and cumulative time of effective infection in the winter–spring tomato cultivation greenhouse, the first occurrence was confirmed three days after the third dangerous judgment. Therefore, it is suggested that this method can predict the risk of infection by B. cinerea at an early stage.