Development of brown rot epidemics in Spanish peach orchards

A new approach to modelling epidemics of brown rot caused by Monilinia spp. in Ebro Valley peach orchards has been developed. This compartmental model was subdivided according to the phenological stages in which the disease can develop (blossom, immature fruit, and ripe fruit). Information host susceptibility, primary and secondary inoculum sources and latent infections in immature fruit was taken into account. The compartmental model is described by a system of differential equations, and is simple enough to allow an analytical study of the main epidemiological factors that determine the rate of disease progress during a single growing season. The proposed model fits well to the epidemic pattern of brown rot observed in northeastern Spain. The transmission of the disease as a nonlinear term implied that small changes in the infection rate had a large effect on the development of the disease. The model has confirmed the usefulness of removing mummies (infected fruit that remains in the crop during winter) from the field to reduce the final incidence of the disease. In addition, all control measures that reduce the rate of secondary infection in ripe fruit, either through the use of more resistant varieties or the use of fungicides, are effective in reducing brown rot incidence. The proposed epidemic model is flexible and allows to add complexities to the system and evaluate the effectiveness of different control strategies.