FLAVID 3 - Investigating presence and genotype diversity of Flavescence dorée phytoplasma in Swiss agricultural and forest ecosystems

A joint research project by WSL Cadenazzo, Agroscope, and Agridea.

“Flavescence dorée” (FD) is a harmful grapevine disease associated with the quarantine organism ‘Candidatus Phytoplasma vitis’ (FDp), which may survive in the landscape on deciduous woody species such as black alder (Alnus glutinosa) as well as on gone-wild grapevines.

The epidemic FDp transmission in vineyards is due to its principal vector, the Nearctic leafhopper Scaphoideus titanus, but several alternative vectors, such as Orientus ishidae, could also sporadically assist in the transmission, especially when vineyards are embedded in more complex landscape contexts. Thus, the epidemiology of FDp may include several actors present across vineyards and seminatural landscape compartments making FD management more arduous and complicated.

In Switzerland (CH), we can distinguish between three different FD situations (see also Figure below): in Southern CH, S. titanus is widespread and FD is endemic across vineyards; in Western CH, S. titanus is present and FDp is spreading among and within vineyards; in Northern CH, S. titanus and FDp are absent in vineyards, but the alternative vector O. ishidae and FDp are present on black alder. Thus, there is an urgent need to improve our knowledge on the distribution of FDp in the landscape and the presence of alternative vectors, and to further develop preventive measures and tools for the early detection.

The overall aim of FLAVID 3 is to better understand the different FDp epidemiology situations in vineyards and seminatural compartments across Switzerland. Our findings will help to refine the monitoring and management of Swiss vineyards and reduce costs related to this quarantine disease for practitioners, as well as national and cantonal authorities.

The project is divided in the following four work packages:

• WP1: Implementation of habitat management approaches to complement current control strategies in areas where FD and S. titanus are established (i.e., FDp endemic, S. titanus widespread; study area: Southern CH);
• WP2: Deepen the understanding of the FD pathosystem in areas where FD and S. titanus are currently spreading (i.e., FDp present and in expansion, S. titanus widespread; study area: Western CH);
• WP3: Assessment of the potential risk of FD and S. titanus arrival and spread in areas currently free of FDp and its vectors (i.e., no FDp in vineyards, S. titanus absent; study area: Northern CH);
• WP4: Assessment of the willingness of Swiss winegrowers to implement control measures for FD eradication and containment (study area: whole Switzerland).