Sharon, R., Northern Research and Development, MIGAL Institute, Kiryat Sh'mona, Israel, Department of Science, Ohalo College, Katsrin, Israel
Harari, A.R., Department of Entomology, ARO, Bet Dagan, Israel
Zahavi, T., Extension Service, Ministry of Agriculture, Kiryat Sh'mona, Israel
Raz, R., Northern Research and Development, MIGAL Institute, Kiryat Sh'mona, Israel
Dafny-Yelin, M., Golan Research Institute, University of Haifa, Katsrin, Israel
Tomer, M., Northern Research and Development, MIGAL Institute, Kiryat Sh'mona, Israel
Sofer-Arad, C., Northern Research and Development, MIGAL Institute, Kiryat Sh'mona, Israel
Weintraub, P.G., Department of Entomology, ARO, Gilat Research Station, Israel
Naor, V., Department of Science, Ohalo College, Katsrin, Israel, Golan Research Institute, University of Haifa, Katsrin, Israel

A stolbur-type phytoplasma is the putative pathogen of grapevine yellows disease that causes economic damage to vineyards in most growing areas around the world. The pathogen is known to be transmitted to vines by two planthoppers, Hyalesthes obsoletus and Reptalus panzer; the latter is found in Europe but has not yet been observed in Israel. The establishment of a vector-pathogen-plant relationship requires that the pathogen and the vector meet on a shared host plant. This does not happen in the ecosystem examined here, where two different principal host plants for the obligate pathogen and its vector exist: the pathogen is established on vines, while its vector, H. obsoletus, develops on Vitex agnus-castus. The present study verified that: (i) the vector cannot complete its life cycle on vines; (ii) V. agnus-castus does not grow in the immediate vicinity of vines, and does not harbour the pathogen; and (iii) the pathogen is not vertically transmitted from mother to offspring. Moreover, in a thorough search of plants in vine growing areas, no other plants were found that host both the vector and the pathogen. However, it was found that the planthopper can acquire the phytoplasma from infected vines. Nonetheless, this does not prove the ability of the planthopper to further transmit the pathogen to vines and does not explain the presence of the vector on the non-preferred vines. Thus, the enigma of the pathogen-vector-host triangle in this system remains unresolved. © 2014 British Society for Plant Pathology.