Epsilon Archive for Student Projects

Abstract

Climate variability, extreme weather, and technological advances are reshaping the global wine industry, expanding viticulture into new regions. Swedish wine production has grown in recent years and gained international recognition; however, growers are now facing damage from the invasive fly Drosophila suzukii. Also known as Spotted wing drosophila (SWD), the fly uses its sclerotized ovipositor to lay eggs in ripening fruit, causing both direct and secondary damage infection that reduce grape quality and wine production. While susceptibility of traditional grape varieties has been studied internationally, little is known about the impact on newer PIWI cultivars. Developed in Germany for fungal resistance, PIWI varieties include some of the most successful grapes grown in Sweden. Differences in berry skin properties, chemical composition, and phenology might influence their susceptibility to SWD. There is therefore a need to monitor the establishment of SWD in Swedish vineyards and to investigate the vulnerability of PIWI cultivars to better understand varietal differences and to develop effective management strategies.
This study aimed to investigate susceptibility factors in five PIWI cultivars, grown under Swedish conditions, to SWD using laboratory non-choice oviposition assays and field monitoring with traps. Results showed that the variety Cabernet cortis was the most susceptible of the five cultivars tested, while Souvignier gris showed strong resistance to oviposition by SWD. Increased oviposition was correlated with decreasing skin resistance (N). No correlations were found between sugar contents and oviposition in this study, even so, observed trends suggest that grape chemical composition requires further investigation. Additionally, the study examined trap catches from fly traps placed in two vineyards in the weeks prior to harvest in southern Scania, Sweden, over two years. Findings indicated a simultaneous increase in trap catches across sites, with fly number rising and falling in relation to temperature fluctuations. Growing degree days (GDD) were used to estimate seasonal generation build-up during and were also associated with increases in trap populations. However, inconsistent handling of trap catches data limit’s reliability, and the results should be considered indicative. Further research is needed to fully understand populations dynamics and infestation levels of SWD in vineyards.