Intercropping Broccoli‐Basil Reduces Aphid Growth: Spatio‐Temporal Modelling Across Scales and Lab Experiments

ABSTRACT Shifting from conventional to sustainable agriculture demands well‐designed experiments and robust analytical models to evaluate agroecological system performance and resilience. We modelled aphid population dynamics in broccoli monocultures and broccoli‐basil intercrops using spatio‐temporal approaches, informed by laboratory experiments on aphid avoidance behaviour. These experiments compared conventional, intensive crop production with sustainable plant protection practices, such as the impact of intercropping on aphid population growth rates. The results revealed that aphids significantly avoided broccoli leaves intercropped with basil, preferring monoculture broccoli. The presence of basil significantly reduced aphid population growth rates, leading to population decline. These findings informed mathematical models integrating plant‐herbivore interactions, aphid movement, diffusion, and repellency. The models employed deterministic approaches, including non‐spatial coupled population dynamics and spatial (1D and 2D) reaction‐diffusion frameworks, simulating aphid dispersal and plant‐aphid interactions over 50 and 100 m domains. Numerical simulations demonstrated that aphids avoid broccoli intercropped with basil, with models capturing basil's repellent effect in a spatio‐temporal context. Simulations revealed cyclic oscillations in plant and aphid populations, stabilising to a steady equilibrium due to spatial population coupling. The spatially explicit approach highlighted how population growth rates, diffusion coefficients, aphid mortality, and spatial domain size influence aphid movement and repellency. Higher diffusion coefficients and lower aphid mortality from other causes amplified the repellent effect of the intercrop system, significantly reducing aphid populations. Our results suggest that broccoli‐basil intercropping enhances pest regulation, offering a sustainable alternative to chemical pest control, although aphid dispersal rates and spatial domain size significantly affect its efficacy.