Epidemiological and mathematical modeling of vascular and wood‑decay pathogens in almond orchards: a conceptual and theoretical analysis
Abstract
Almond decline in Mediterranean and warm temperate areas arises from two distinct but interacting pathosystems: systemic vascular dysfunction caused by Xylella fastidiosa and structural wood degradation caused by fungal species of the Botryosphaeriaceae family. In this research we developed an age-structured multiplicative model for decline that incorporates several interrelated aspects of decline, including infection likelihood, vascular dysfunction, the dynamics of fungal colonization, and the impact of applying chemical control products, to quantify their combined contribution to orchard decline and eventual collapse. Co-infections exhibit a synergistic, accelerating component to their decline, with vascular dysfunction reaching saturation levels early on and therefore strongly limiting orchard life expectancy. Chemical control products such as fungicides, copper and phosphonates significantly lower the effective fungal growth rate and extend the timeline for orchard decline by 1-5 years, but does not eliminate the hydraulic failure in trees infected by Xylella. In fungal‑only systems, application of chemical controls significantly reduces the rate of decline trajectories and enhances orchard longevity. Our model describes the physiological processes that lead to increased decline rates in mixed infections and provides a quantitative framework for evaluating management strategies. Because X. fastidiosa is absent from Greece, the model is developed as a conceptual and theoretical framework grounded in published physiological and epidemiological data.
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DOI: https://doi.org/10.33804/pp.010.05.6245
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