Dynamics of Spore-Producing Plant Pathogenic Fungi in Agricultural Environments

This paper proposes an original mechanistic modeling framework describing the nonlinear interactions between plant biomass, mature fungal populations, and the free spore compartment within an agrosystem. The novelty of this formalism lies in the explicit integration of the pathogen’s ontogenetic cycle, thereby capturing the critical feedback of the spore reservoir on infection dynamics. A rigorous qualitative analysis establishes that the system is mathematically well-posed, with solutions evolving within a compact and positively invariant set. A global sensitivity analysis, based on the Extended Fourier Amplitude Sensitivity Test (eFAST) method, identifies the intrinsic growth rate of the resource, resource mortality, and the exogenous flux of propagules as the pivotal parameters dictating the resilience of plant biomass. In particular, the intrinsic growth rate emerges as a key driver not only of resource regeneration but also of epidemic amplification through increased host availability. An investigation of the equilibrium states reveals a stability structure governed by a critical invasion threshold, Rinv. A major theoretical contribution of this study is the identification of a backward bifurcation. This phenomenon suggests the existence of a bistability region where simply reducing the basic reproduction number below unity proves insufficient to guarantee pathogen eradication, highlighting the significance of the initial inoculum load. Numerical simulations corroborate the complexity of the phase space, revealing the emergence of limit cycles and sustained oscillations. Finally, this work evaluates targeted control strategies, demonstrating that, in addition to reducing spore production and limiting external inputs, regulating the intrinsic growth rate of the resource constitutes a critical and nonintuitive control lever. Indeed, excessive growth may inadvertently enhance pathogen proliferation by increasing the pool of susceptible hosts. These results highlight the need for integrated management strategies combining inoculum control with optimized plant growth conditions in order to effectively contain epidemic spread and restore agricultural productivity.