Monitoring of alternative insect vectors of “flavescence dorée’-related phytoplasmas in different wine-growing regions in Germany

“Flavescence dorée” (FD) is a threatening disease of grapevine associated with phytoplasmas of the 16SrV ribosomal group and is epidemically spread within vineyards by the Nearctic leafhopper Scaphoideus titanus. However, recent studies demonstrated that the spread of FD is not only related to this pathosystem but may include alternative vectors and reservoir plants. Alders have been shown harbouring different 16SrV-strains that can be transmitted from alder to alder by Orientus ishidae and Allygus spp., and by O. ishidaealso from alder to grapevine. In all cases the Map-FD2 strain M38 was transmitted. Therefore, a monitoring for both leafhopper species collected on alders has been conducted over 5 years in different wine-growing regions in Germany to investigate their occurrence and infection status. O. ishidae individuals naturally infected with strain M38 were captured in all regions except Mosel. Allygus spp. were also infected with strain M38 but harboured in addition several other non-epidemic strains. Both species captured in Württemberg were able to transmit strain M38 to alder test plants. The results indicate that the widespread occurrence of O. ishidae infected with the epidemic “flavescence dorée” strain M38 represents a risk for the spread of “flavescence dorée” in regions that are so far free from FD.