Disentangling the Effects of Intercropping on Vector-Borne Plant-Virus Dynamics

Emerging plant diseases threaten crop yields, food security, and the health of ecosystems. In fields with multiple plant species, disease management can become challenging, as different crops can either reduce or increase virus transmission. Motivated by empirical evidence that intercropping can limit virus spread, we develop a mathematical model that integrates the epidemiological dynamics of multiple crops and an insect vector. We derive an explicit expression for the basic reproduction number, showing how infectivity rates and crop composition together determine whether a disease will persist or die out. We also derive a threshold index to assess the potential for transient outbreaks, even when long-term disease persistence is unlikely. We compare monocultures with intercropped systems and find that intercropping does not always reduce disease risk, where, under some conditions, it can actually enhance virus spread. Finally, we explore how crop diversity may shape the evolution of vector host preferences, potentially altering long-term disease risks. These results have practical implications for designing intercropping systems that minimise virus transmission while avoiding unintended amplification effects, providing a theoretical foundation for sustainable and effective plant disease control.