Potential effects of climate change on distribution and activity of insect vectors of grapevine pathogens

The impact of changing climatic conditions on viticulture is currently mainly discussed with respect to alterations in grape physiology, adaptation of cultivars and cultural practice. However, pests and diseases of grapevine are influenced by changing climate, too. They are affected either directly through impacts on their life history and epidemiology or indirectly by changes of grapevine physiology and phenology. This presentation will focus on potential risks of changing climate caused by arthropod vectors of grapevine pathogens particularly in cool climate viticulture of the northern viticultural areas of Europe. More or less complex pathosystems consisting of grapevine, pathogens, vector(s) and sometimes alternative host plants need to be considered, particularly since the respective pathogens are graft transmissible and may be spread independent from their vectors by propagation material. Known arthropod vectors in European viticulture belong to the order Hemiptera. They transmit either grapevine viruses (Coccoidea; soft scales and mealybugs) or phytoplasmas (Auchenorrhyncha; leafhoppers and planthoppers). Many are Mediterranean species that depend on high ambient temperatures and are not yet present or restricted to greenhouses or to sites with favourable microclimatic conditions in the northern viticultural regions. Rising temperature could increase the risks of introduction of vectoring species such as virus transmitting mealybugs or may lead to an extension of their natural range to the North. This is currently happening with the leafhopper Scaphoideus titanus, the vector of Flavescence dorée. Other species with possibly benefit grow an increase in their population density and an extension of the plant host range or suitable habitats, which might result in a higher vectoring activity. Transmission of Ampelo-and Vitiviruses by soft scales and of Bois noir phytoplasma by the planthopper Hyalesthes obsoletus are examples for this scenario. The examples presented here are based on field observations. Detailed studies would be necessary to reliably describe the effects of climate change and to assess the risks. An interdisciplinary approach, bringing together the expertise of biologists, plant pathologists and meteorologists, could help to investigate these interactions more extensively. A more detailed knowledge of the major environmental factors that influence the particular pathosystems could help to develop tools to scale down risk assessment to individual viticultural areas.