An epidemiological model to predict infection of loquat scab caused by Fusicladium eriobotryae

Fusicladium eriobotryae (Cav.) Sacc. is the causal agent of loquat scab, which is the main disease affecting loquat (Eriobotrya japonica Lindl.) in the Mediterranean basin. F. eriobotryae infects leaves, shoots and fruits; scabby fruits are unsuitable for the market, resulting in significant economic losses. To predict the infection of loquat fruits, a mechanistic, weather-driven, disease model has been developed. By simulating conidial infection processes following a rain event, the model estimates the percentage of conidia that successfully infected loquat fruits at the end of an infection period; input data are hourly values of air temperature, rainfall, relative humidity and leaf wetness. The model is mainly derived from equations developed from recent in vitro and plant experimental results. Three data sets have been used to validate the model: (1) percentage of affected fruit in an unsprayed loquat orchard during two growing seasons (2011 and 2012); (2) infection occurrence in an unsprayed loquat orchard during 2013; and (3) expert appreciation of disease level on seven loquat growing seasons (expert elicitation). Results from this validation showed that the model is able to predict the infection periods and the development of the disease. The model could be used to improve the timing of fungicide sprays, thus reducing the number of applications.