Dominant cixiid vector and transmission of 'Candidatus Arsenophonus phytopathogenicus' and 'Candidatus Phytoplasma solani'-related strain 16SrXII-P in sugar beet in Austria.

The presence of fastidious phytopathogenic bacteria 'Candidatus Arsenophonus phytopathogenicus' and 'Candidatus Phytoplasma solani' challenges sugar beet cultivation in Austria. Reptalus artemisiae (Becker, 1865) (referred before as Reptalus quinquecostatus sensu Holzinger et al. 2003) is the principal vector of 'Ca. P. solani' to sugar beet in Serbia, while Pentastiridius leporinus is the primary vector of 'Ca. A. phytopathogenicus' in western Europe and can also transmit 'Ca. P. solani'. This study investigates the epidemiology of the associated diseases in Austrian sugar beet fields. An extensive survey in 2024 at 33 locations revealed significant spatial and temporal variability in cixiid populations, with R. artemisiae emerging as the predominant species. Transmission trials and field surveys confirmed R. artemisiae as a vector of 'Ca. A. phytopathogenicus' and 'Ca. P. solani' 16SrXII-P driving a disease outbreak in Nikitsch. The predominance of R. artemisiae in nearly all monitored fields suggests its significant role in the pathogens' epidemiology on a broader scale in the Pannonian plain. Spatial and temporal variations in pathogen incidence in Austrian sugar beet mirror patterns in Serbia, driven by R. artemisiae. The co-occurrence of 'Ca. A. phytopathogenicus' and 'Ca. P. solani' 16SrXII-A and 16SrXII-P and their transmission by two vectors complicate disease management efforts.