International audienceFlavescence dorée is a serious disease for European vine growers. Indeed, Flavescence dorée causes yield losses and lower grape quality. As a consequence, Flavescence dorée is costly and needs advanced control strategies. For instance, in 2005, 34 million Euro was given to Italian vine growers to compensate losses due to the disease. The infection by Flavescence dorée results from the association of a phytoplasma and the leafhopper vector, Scaphoideus titanus. Despite mandatory controls using insecticides, Flavescence dorée is still spreading in Europe. Here, we review the biology and ecology of S. titanus to suggest improved management techniques. The main findings are as follows. (1) The long-distance spread of S. titanus is mainly due to human activities, and all European vineyards are susceptible to be colonized. (2) S. titanus is an efficient vector because it can reach a high population level and it is specific to Vitis spp. (3) Current control and prophylaxis are insufficiently effective. (4) Variation in vector populations and vector capacities lead to differential risks of plant infection. Factors driving such population variations could be modeled to improve S. titanus control. (5) Feeding behavior is a key factor in the phytoplasma–vector relationship. (6) The infection risk is mainly limited by vector control. To decrease pesticide use, a cross survey of the vector population and of the infected stocks triggers mandatory treatments. (7) Alternative sustainable methods or strategies are required to reduce insecticide use and increase control efficiency. In the short term, new models could support the establishment of more sustainable pest management operations. In the long term, innovative techniques involving symbionts, mating disruption and a push–pull strategy could improve S. titanus and Flavescence dorée control with less environmental impact

The leafhopper Scaphoideus titanus is the vector of a major phytoplasma grapevine disease, Flavescence dorée. The vector's distribution is in Eastern and Northern Europe, and its population dynamics varies as a function of vineyard latitude. We tested the hypothesis that hatching dynamics are cued by cold temperatures observed in winter. We exposed eggs from a natural population to simulated "cold" and "mild" winters and varied the exposure time at 5°C from 0 to 63 days. We show that temperature cooling mainly affected the onset of hatching and is negatively correlated to the cold time exposure. The majority of hatchings occurred more quickly in cold rather than in mild winter simulated conditions, but there was no significant difference between the duration of hatching of eggs whatever the cold time exposure. In agreement with the Northern American origin of the vector, the diapause termination and thus the timing regulation of egg hatching require cold winters.

Transmission trials were carried out using Reptalus quinquecostatus (Cixiidae), a potential vector of 'Candidatus Phytoplasma solani' ('Ca. P. solani'), to assess its ability to inoculate the phytoplasma to periwinkle (Catharanthus roseus), grapevine (Vitis vinifera), lavandin (Lavandula × intermedia) and tobacco (Nicotiana tabacum). Detection, genotyping and comparison of 'Ca. P. solani' strains carried by R. quinquecostatus showed that R. quinquecostatus carried a higher diversity of 'Ca. P. solani' than Hyalesthes obsoletus, major known vector of 'Ca. P. solani' strains. Molecular analyses also showed the presence of a new strain only in grapevines and R. quinquecostatus. 'Ca. P. solani' was successfully inoculated to periwinkles by R. quinquecostatus, but no transmission was achieved to the other tested plants. The ability to transmit 'Ca. P. solani' to plants and observations of adults feeding on grapevines in vineyards consolidate the hypothesis that R. quinquecostatus is a specific vector of 'Ca. P. solani' strains. Moreover, the discovery of a new genotype present in R. quinquecostatus and not in H. obsoletus, vector also present on grapes, suggests that R. quinquecostatus should have a direct role in 'Ca. P. solani' epidemiology. Overall, even if R. quinquecostatus has a minor or no role in 'Ca. P. solani' transmission from weeds to grapevines, it can have an indirect role in Bois Noir epidemiology. This planthopper can contribute to maintain an alternative 'Ca. P. solani' cycle in weeds even in the absence of H. obsoletus preferentially by maintaining pathogen reservoirs in wild compartments neighbouring susceptible crops.

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