A Survey of Non-crop Plants as Alternative Hosts to Raspberries for Drosophila suzukii (Spotted Wing Drosophila)

The spotted wing fruit fly (SWD), Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is a pest of small fruit crops. Unlike most other Drosophila species, this insect can oviposit into ripe fruits, rendering them unmarketable. Drosophila suzukii is spreading quickly throughout the continental United States including South Dakota, and causing serious damage to horticultural crops, particularly those within the fruit industry. This study determines the D. suzukii host plant both commercial crops and native plants, and defines non-crop host plants by season in South Dakota. Further, it confirms the occurrence of the fly in southeastern South Dakota and identifies high-risk infestation areas in raspberry crops. Results show peak captures of adult populations in the middle of the summer (July) and through the autumn season. Lonicera tatarica Linneaus (honeysuckle), Celtis occidentalis L. (hackberry), Morus alba L. (mulberry), Rhamnus cathartica L. (buckthorn) and Symphoricarpos albus L. (snowberry) are non-crop host plants and had the highest yield of D. suzukii adults from summer to autumn. This indicates that late season fruit crops or varieties could be at risk of D. suzukii fruit injury in this area. Non-crop and commercial late fruit crops, including fall-bearing raspberries are generally harvested when D. suzukii populations remain high in this region. The number of captured adult insects was related between female and male populations of the sampled sites based on their total number flies. The number of females was generally higher than the number of males during the season. This survey also reports non-crop host plants in eastern South Dakota, suggesting that they affect crop risk for higher numbers of D. suzukii. Finally, the presence of these non-crop host plants is likely important for understanding D. suzukii management strategies.