STREP: a brown-spot disease predictor for scheduling fungicide sprays against Stemphylium vesicarium on pear

Abstract

Brown spot of pear (Pyrus communis) caused by Stemphylium vesicarium is an important disease in fruit-growing areas of Europe. The control of brown spot is based on protectant sprays of fungicide applied, at 7- to 15-day intervals depending on the type of fungicide, from fruit set to preharvest regardless of the risk of infection. A forecasting model has been developed and can be used for timing the fungicide applications and to eliminate unnecessary sprays. The model quantifies the relationship between wetness duration and temperature in disease severity and can be used as a tool for the prediction of disease infection periods. The capacity of risk prediction was validated over 2 years. The fungicide sprays scheduled by the STREP forecaster were evaluated in commercial orchards during 3 years in different climatic areas in Spain and Italy. The results showed consistently that use of the STREP model minimized the number of fungicide sprays compared with a protectant schedule, but without decreasing the quality of commercial disease control. The susceptibility of selected European pear cultivars to infection by S. vesicarium and the influence of fruit age were also determined. The implementation of the model in warning stations will require the combination of predictions by the STREP model, the level of inoculum and the sensitivity of phenological stage and pear cultivar.