Survey of populations of the planthopper Hyalesthes obsoletus Sign. (Auchenorrhyncha, Cixiidae) for infection with the phytoplasma causing grapevine yellows in Germany

H. obsoletus is the vector of grapevine yellows (Vergilbungskrankheit, VK) in Germany. Monitoring the abundance of the vector populations and their infestation with the phytoplasma associated with VK is necessary to assess the risk of disease outbreaks and field‐spread. We tested planthoppers collected in four different vineyards of the Mosel River valley in Germany for infection by VK using DAS‐ELISA and PCR. ELISA readings of female planthoppers were significantly higher than those of males. The proportion of positive testing H. obsoletus was higher in PCR tests compared to ELISA. The trapping method, either sweep‐net or sticky‐trap, had no significant influence on the proportion of planthoppers that reacted positively in PCR tests. The infestation of vineyard populations estimated by PCR varied between 7% and 34%. Batch samples, prepared from mixtures of crude planthopper extracts or from groups of 25 planthoppers, proved to be reliable for the detection of a single infected vector. For routine monitoring, we suggest PCR tests of batch samples from sticky traps.