New problems for old vineyards: Mitigating the impacts of yellow-legged hornets ( Vespa velutina ) in a historical wine-producing area

Traditional small-sized vineyards are especially sensitive to different impacts, including the arrival of new pests. The adults of the yellow-legged hornet (Vespa velutina), an invasive alien species present in the Iberian Peninsula since 2010, feed on sugary foods, causing crop losses in vineyards. However, present management techniques for the control of V. velutina are limited, and they do not provide effective control in agricultural settings. This work aims to evaluate the use of an exclusion system in a traditional non-mechanized vineyard of a highly invaded area by V. velutina in NW Spain (Protected Geographical Indication of Betanzos, Galicia) as a method to mitigate the damage caused by hornets. Anti-hail nets were used in a factorial design experiment with groups of netted and unnetted vines of two white wine cultivars in order to address the vineyard production loss. In particular, we aim to 1) asses the effectiveness of anti-hail netting on preventing grape yield loss, 2) assess the impact of antihail netting on grape ripening and incidence of bunch fungal infection, and 3) study the potential relationship between the damage caused by V. velutina and grape fungal diseases. Results show that the tested exclusion system increases the crop yield, since it prevents effectively both the damage caused by hornets and birds. No significant correlation between the damage caused by V. velutina and the incidence of bunch fungal diseases was found in either cultivar. However, netting increased slightly the final sugar content in one of the cultivars, as well as the incidence of bunch fungal damage. We discuss the management implications of this exclusion method within the framework of agricultural land abandonment and the loss of traditional landscapes.