Host plant specificity of Hyalesthes obsoletus and consequences for “bois noir” epidemiology

The complex epidemiological system of grapevine “bois noir” (BN) consists of stolbur (16SrXII-A) phytoplasma associated with the disease, the vectoring planthopper Hyalesthes obsoletus, and wild herbaceous host plants of the pathogen and the vector. Severe outbreaks of BN that occurred in Germany since 2004 are assumed to be related to the exploitation of a new host plant by the vector and the spread of a host-specific type of the phytoplasma. This paper confirms the association of tuf-type I of the BN phytoplasma with the recent BN outbreaks in Germany and the restriction of different BN-types to specific host plants. Mitochondrial DNA analysis of H. obsoletus from different European countries and Israel demonstrated a recent demographic expansion and circum-alpine immigration of H. obsoletus to Germany, and RAPD analysis revealed differences between host plant populations.