Does myrtle rust hijack insect sensory biases? Colours and scents of the plant pathogen Austropuccinia psidii

Many plants sharing pollinators evolve similar floral traits—such as colour, shape, and scent—in response to pollinators’ sensory preferences. Other taxa, including fungi, can also employ or exploit insect sensory ecology to aid dispersal. The plant pathogen Austropuccinia psidii (causative agent of myrtle rust) produces bright yellow-orange spores on Myrtaceae hosts, resembling pollen to the human eye. It is actively collected by honey bees (Apis mellifera), and recent findings suggest that these spores offer nutritional value to bees. Here, we investigate whether A. psidii spores resemble floral guides (colour and odour) to attract insect vectors for dispersal. By analysing spore colour, brightness, and contrast when modelled into honey bee, hoverfly, and fly vision systems, we demonstrate that A. psidii spores exhibit visual cues similar to pollen. Our findings suggest A. psidii may exploit insect sensory systems, mirroring plant-pollinator interactions to enhance transmission. This study uncovers a previously overlooked ecological dynamic, where plant pathogens may co-opt pollinator-mediated dispersal pathways.