Coupling epidemiological and tree growth models to control fungal diseases spread in fruit orchards

Abstract

Agronomic practices can alter plant susceptibility to diseases and represent a promising alternative to the use of pesticides. Yet, they also alter crop quality and quantity so that the evaluation of their efficacy is not straightforward. Here we couple a compartmental epidemiological model for brown rot diffusion in fruit orchards with a fruit-tree growth model explicitly considering the role of agronomic practices over fruit quality. The new modelling framework permits us to evaluate, in terms of quantity and quality of the fruit production, management scenarios characterized by different levels of regulated deficit irrigation and crop load. Our results suggest that a moderate water stress in the final weeks of fruit development and a moderate fruit load provide effective control on the brown rot spreading, and eventually guarantee monetary returns similar to those that would be obtained in the absence of the disease.

Figure 1

Expected performances of the 54 considered scenarios, in the presence and absence of the disease, with respect to three different management objectives: maximizing total yield mass, average fruit mass, fruit sweetness index. (“jitter” function was used to separate overlapping points and increase legibility).

Figure 2

Expected performances of the 54 considered scenarios, in the presence and absence of the disease, with respect to monetary revenue.

Figure 3

Estimated surfaces showing expected monetary revenue in the absence of the disease (A), in the presence of the disease (B), monetary losses due to the disease (C), as a function of initial crop load CL and water potential in the last five weeks of fruit growth.