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

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.

Data on Swiss fruit and wine growers' management strategies against D. suzukii, risk preference and perception.

The survey data presented in this article provides information on risk management strategies in response to the invasive pest Drosophila suzukii (spotted wing drosophila) collected among Swiss fruit and wine growers. The survey covered grape, plum, berry and cherry growers and the years 2016, 2017 and 2018. Strategies to prevent or control Drosophila suzukii were collected at the variety level and information on perceived infestation levels as well as harvest losses was collected. In total, nine surveys were conducted, creating a unique panel dataset. Additionally, data was collected with regard to fruit growers' characteristics (e.g. age, gender) and farm characteristics (e.g. farm size, farm-level workforce, succession, insurance use). Risk preferences were elicited via a self-assessment of risk preferences and (for selected surveys) using a multiple price list. Additionally, (for selected surveys) locus of control and self-efficacy were evaluated via self-assessment questions.

Management strategies against Drosophila suzukii: insights into Swiss grape growers choices.

BACKGROUND: In 2017, we investigated measures adopted by Swiss grape growers in response to Drosophila suzukii by conducting a survey presenting information obtained from 372 growers on 1708 vineyards. RESULTS: We found the strategies adopted to be heterogeneous and largely dependent on grape variety (table vs. wine grapes). We identified six clusters of control methods to combat D. suzukii, the most important of which involves using a combination of control methods such as insecticides, mass trapping and sanitation measures, especially pinching of foliage or mowing and mulching. Grape growers in our sample rely primarily on information from public institutions or other growers and the majority plan to continue taking sanitation measures to combat D. suzukii. CONCLUSION: Our results suggest that strategies adopted in Switzerland differ widely, not only between growers, but also at a vineyard and regional level. Thus, policies and extension services should be targeted (e.g. to varieties and regions) and tailored to types of growers. We find that preventive measures are important when combatting D. suzukii and can reduce post-infestation measures such as pesticide usage. In our sample, biological insecticides, such as kaolin, played a vital role in the control of D. suzukii and merit further support. © 2019 Society of Chemical Industry.