Disease regulation in intercropping systems depends on spatial arrangement – A modelling study

Cultural diversification is presented as an effective method to increase the resilience of agrosystems in the face of climate change and the need to reduce reliance on artificial inputs. In particular, there is a growing interest in understanding how diversified cultures can help in reducing pesticide use. In the case of intercropping, specific mechanisms have been identified which impact disease development: dilution and barrier effects as well as changes in microclimate in the canopy, but they are hardly characterised. We propose a process-based modelling approach to study a virtual wheat/pea intercrop submitted to a brown rust epidemic, coupling two previously validated models. We thus deciphered in silico the effect of dilution, barrier and microclimate mechanisms and their sensitivity to changes in spatial arrangement of the field. We found that in 93% of cases, intercropping reduced disease, by up to half with 60% wheat. Moreover, intercropping had overall beneficial effects in terms of disease control by protecting the photosynthetic capacity of wheat for 37 days longer on average. Furthermore, barrier and dilution effects counteracted the adverse microclimate throughout the crop cycle. Given the complex interactions between spatial arrangement and interannual variability, we argue that modelling is a valuable tool to run multiple simulations, identify scenarios most conducive to effective disease protection, and provide a reflexion on further research directions. • Coupled models highlight complex mechanisms of disease regulation in intercrops. • Intercropping significantly delays the disease onset compared to sole cropping. • The main benefit in disease control when intercropping is its barrier effect. • Increasing the distance between rows was the most influential agronomic lever. • Intercropping's unfavourable microclimate is offset by barrier and dilution effects.