The economic impact of Drosophila suzukii : perceived costs and revenue losses of Swiss cherry, plum and grape growers

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BACKGROUND: Drosophila suzukii can lead to substantial damages in horticultural production. In this article we analyze revenue losses and cost increases due to D. suzukii as perceived of Swiss cherry, plum and grape growers. Moreover, we investigate associations between farm and grower characteristics and revenue losses and perceived costs increases. We surveyed Swiss growers of cherries, plums and grapes repeatedly in the period 2016-2018 (N = 1572). RESULTS: We find that 76% of cherry, plum and grape growers faced additional costs due to D. suzukii. In contrast, yield losses due to D. suzukii infestation were small on average, but nevertheless high for some growers. We find substantial heterogeneity in perceived costs and revenue losses across crops, years and farms. Larger farms are found to face lower perceived additional costs, suggesting scale effects in prevention and control of D. suzukii. Growers with a higher inter-varietal diversity perceived additional costs to be higher. Furthermore, organic farming was negatively associated with expected additional costs. CONCLUSION: Our results suggest that the economic impact of invasive species such as D. suzukii goes far beyond reductions in yield quantity and quality, but rather stems from higher costs due to the need to establish preventive and control measures. Heterogeneity in costs and revenue losses suggests that policy measures to support growers need to be tailored to crops and farm types. Policies supporting improvements of measures against D. suzukii and other newly occurring alien pests and reduce additional costs such as more efficient preventive and control measures merit further encouragement.

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