Spotted wing drosophila (Drosophila suzukii, SWD) is an invasive pest of soft-skinned fruits that has been detected throughout the United States in the last few years.

Initial detection and spread

SWD was first detected in the United States in central California in 2008. It was not correctly identified until early 2009 and was detected in fruit crops from California to Washington by the end of the year. SWD was first detected in the eastern United States in Florida in late Fall 2009, near the main strawberry producing area. A volunteer-based SWD detection network was responsible for the first SWD detections in NC, VA, WV, MD, and AR and first detection at agricultural sites in SC. SWD has since been detected throughout the United States, Canada, Mexico, and several European countries.

States with confirmed spotted wing drosophila detentions and detection year. Figure adapted from Burrack, et al. 2012.

Potential economic impacts of SWD

SWD attacks a wide range of soft-skinned fruits including blueberries, caneberries, cherries, grapes, strawberries, and their wild relatives. There is currently a zero tolerance threshold for SWD larvae in fresh market fruit sold in the United States and a single infested fruit can result in the rejection of an entire shipment. This means that SWD has the potential to negatively impact small fruits industries in many states and may even threaten the viability of some industries. In the United States, SWD severely threatens the viability of berry production, most significantly impacting caneberries (raspberries and blackberries), blueberries, and strawberries, as well as cherries.

Small fruits are high value crops, and potential losses may be high. For example, after SWD was widely detected in California, researchers estimated that potential crop losses in strawberries, cultivated blueberries, caneberries, and cherries could be as high as $511 million annually in California, Washington, and Oregon. The total farmgate value for these crops in 2008 was estimated to be $2,577 million, based on data collected by the National Agricultural Statistics Service (Bolda et al. 2010). However, potential crop loss statistics were lacking for the eastern United States.

Potential crop losses in the eastern United States were estimated by the eFly Working Group at a meeting in Raleigh, NC in September 2012. Potential losses in reporting states in 2012 equaled $207 million, based on maximum observed losses and crop values in cultivated and wild blueberries, caneberries, and strawberries. Potential loss data were reported from AR, CT, GA, FL, ME, MI, NJ, NY, NC, PA, SC, and VA. The total crop value for these crops in reporting states was estimated to be $567 million. Cherries are valued at over $40 million in the eastern US, but the 2012 crop was significantly damaged due to late freeze injury. Therefore, cherry totals were not included.

*SC and VA not included, **Only ME, +AR, SC, and VA not included, ^AR and VA not included

Measures of actual crop loss on state or regional scales were also lacking for both the western and eastern US. Such data have been difficult to obtain for several reasons. First, SWD damage can be hard to detect because some fruits that are infested with eggs and young larvae can still look healthy and edible. Second, damaging populations can build up quickly in commercial fields because adults can reach sexual maturity within two days of emergence and females can lay 300+ eggs each. Finally, available traps and baits are not effective at predicting infestation and several researchers have discovered infested fruit in fields where no flies were caught in traps. All together, these issues have made it difficult to put a price tag on the economic losses caused by SWD and to estimate the full economic impact of SWD in the United States.

The eFly Working Group assessed measurable loses across several crops in the eastern US.

Cultivated blueberries

*USDA NASS Noncitrus Fruits and Nuts Summary and/or ERS Summaries, 2011-2012, ⁺Excluded from totals because crop value data not available, ^University of Florida crop value estimates.

Wild blueberries

*USDA NASS Noncitrus Fruits and Nuts Summary and/or ERS Summaries, 2011-2012

Caneberries (blackberries and raspberries)

⁺Excluded from totals because crop value data not available. ⁺⁺Excluded because loss estimates not reported. ^NC State University Department of Horticulture estimate.

Strawberries

⁺Excluded from totals because crop value data not available. ^University of Georgia  Cooperative Extension estimate. ^^Clemson University Cooperative Extension estimates; nearly all strawberries sold directly to the consumer or to other farm stands at a price considerably higher than the published wholesale market price.

Additional, limited loss data for grapes, cherries, and peached along with case studies from 2012 is available in the full report.

A future goal of the eFly Working Group is to contextualize SWD impacts beyond crop losses and input increases. There has been some effort in the western US to incorporate pesticide use costs, labor increases for sanitation, and price elasticity (specifically potential price increases if crop availability decreases) into SWD impact assessments (Goodhue, et al. 2011). Other potentially important, but as of yet unexplored, aspects of losses due to SWD include:

• Reduction in value from fresh market to processing or juice
• Shipping costs for fruit that is later rejected
• Market reduction due to pesticide limitations
• Rejection of pesticide treated fruit by direct market or you-pick customers
• Losses of long term contracts, packing costs for rejected fruit
• Repacking costs for shippers
• Increases in quality control staffing and labor
• Equipment and labor costs for pesticide applications
• Loss of harvester jobs at impacted farms
• Siphoning of extension and research resources from previous priorities
• Elevation of non target pests along with their associated management
• Delays in releases of new varieties because of limited markets or inability collect useful field data

You can help!

Gathering information about the impact of SWD in fruit crops is very important. If you or someone you work with were affected by SWD during the past year, please consider taking the 2013 SWD Impact Assessment Survey. Ultimately, your input will help us to contextualize SWD loss data in a more meaningful fashion, to prioritize research objectives, and to better manage SWD in the eastern United States.

More information

Bolda, M.P., R.E. Goodhue, F.G. Zalom. 2010. Spotted wing drosophila: potential economic impact of a newly established pest. Agric Resource Econ. Update, Univ. Calif. Giannini Foundation Agric. Econ.

Burrack, H.J., P. Smith, D. Pfeiffer, G. Koehler, J. LaForest. 2012. Using Volunteer-Based Networks to Track Drosophila suzukii (Diptera: Drosophilidae) an Invasive Pest of Fruit Crops. Journal of Integrated Pest Management

Goodhue, R.E., M. Bolda, D. Farnsworth, J.C. Williams, F.G. Zalom. 2011. Spotted wing drosophila infestation of California strawberries and raspberries: economic analysis of potential revenue losses and control costs. Pest Management Science