Disease-suppressive mechanisms in contrasting potato-based strip-cropping systems

Intercropping has been shown to suppress diseases in many crop-pathogen combinations and could be a component of more sustainable integrated crop protection. While various disease-suppressive mechanisms have been proposed, it remains unclear how different companion species influence these mechanisms, and whether trade-offs or synergies exist between them. Field experiments were conducted in the Netherlands to study various disease-suppressive mechanisms affecting late blight epidemics in potato strip-cropped with contrasting companion crops (grass, faba bean, or maize). Strip cropping significantly altered the microclimate in the potato strip; relative humidity was lower in potato-grass than in the potato monoculture, whereas the humidity was increased in potato-maize, especially later in the season. Strip cropping with faba bean did not significantly change the microclimate. Furthermore, potato-maize intercropping received the lowest number of particles over the growing season (a proxy for incoming spores). Strip cropping had little to no effect on potato plant morphology or canopy structure. Grass as a companion created drier conditions in the neighbouring potato canopy making it less conducive for disease development, while maize formed a barrier for spore dispersal though it increased humidity later in the season. But the barrier strategy appears a less certain approach across growing seasons, as it relies on the companion crop reaching sufficient height before the epidemic begins, but the timing of the epidemic is unpredictable and may be very early. This study offers insights into how companion species with specific traits can assist disease control in strip cropping.