The Spotted-wing Drosophila (SWD) is an invasive pest native to Southeast Asia. Since it was first detected in 2008 in California, the fly has rapidly become widespread throughout North America. Unlike other common drosophila species breeding on rotting fruits, SWD female has a large and serrated ovipositor (Fig. 1) that enables it to lay eggs inside ripe and fresh fruits. As the fruit ripens, often after harvest, damage caused by SWD (dimples and craters on the skin of the fruit) becomes visible (Fig. 2). SWD is highly polyphagous; being able to oviposit and/or reproduce in various cultivated and wild fruits. Its fast development and high reproductive potential can lead to explosive population increases and significant economic losses to crops. Economic losses from SWD in the western US for raspberries, blackberries, blueberries, strawberries, and cherries are estimated to be up to $500 million annually1. Current control programs rely heavily on insecticides that target adult flies in commercial crops. Because non-crop habitats can act as a reservoir for the fly’s reinvasion into treated crops, area-wide IPM strategies such as biological control that reduce population densities at the landscape level need to be developed for such a highly mobile and polyphagous pest.
Because of the low parasitism by resident parasitoids and especially the lack of larval-attacking parasitoids, Dr. Wang and other scientists (see references 2-3) traveled to part of the native range of SWD, China and Korea, to look for more effective and host-specific parasitoids. In Asia, they have discovered at least 13 larval parasitoid species, with mean parasitism rates as high as 19% in South Korea and 30% in China2-3. Due to the promising higher rates of parasitism, several candidate larval parasitoids have been imported into the University of California Berkeley and USDA ARS Newark quarantine facilities for systematic evaluations on their biology and efficiency against SWD, host specificity, climate adaptability as well as potential interspecific interactions (competition) among different parasitoids. For example, Dr. Wang et al. (2019a,b) have compared the fecundity and host stage preference, and examined potential interspecific competition among three most promising Asian larval parasitoids, among other factors tested4-5.
- Farnsworth, D., Hamby, K. A., Bolda, M., Goodhue, R. E., Williams, J. C., & Zalom, F. G. (2017). Economic analysis of revenue losses and control costs associated with the spotted wing drosophila, Drosophila suzukii (Matsumura), in the California raspberry industry. Pest management science, 73(6), 1083-1090.
- Daane, K. M., Wang, X. G., Biondi, A., Miller, B., Miller, J. C., Riedl, H., ... & van Achterberg, K. (2016). First exploration of parasitoids of Drosophila suzukii in South Korea as potential classical biological agents. Journal of pest science, 89(3), 823-835.
- Giorgini, M., Wang, X.G., Wang, Y., Chen, F.S., Hougardy, E., Zhang, H.-M., Chen, Z.-Q., Cascone, P., Formisano, G., Carvalho, G.A., Biondi, A., Buffington, M., Daane, K.M., Hoelmer, K.A., Guerrieri, E. (2019). Exploration for native parasitoids of Drosophila suzukii in China reveals a diversity of parasitoid species and narrow host range of the dominant parasitoid. Journal of Pest Science, 92, 509-522.
- Wang, X. G., Nance, A. H., Jones, J. M., Hoelmer, K. A., & Daane, K. M. (2018). Aspects of the biology and reproductive strategy of two Asian larval parasitoids evaluated for classical biological control of Drosophila suzukii. Biological Control, 121, 58-65.
- Wang, X.G., Hogg, B.N., Hougardy, E., Nance, A.H., Daane, K.M. (2019). Potential competitive outcomes among three solitary larval endoparasitoids as candidate agents for classical biological control of Drosophila suzukii. Biological Control, 130,18-26.
- Lee, J. C., Wang, X., Daane, K. M., Hoelmer, K. A., Isaacs, R., Sial, A. A., & Walton, V. M. (2019). Biological control of spotted-wing drosophila (Diptera: Drosophilidae)—Current and pending tactics. Journal of Integrated Pest Management, 10(1), 13,1-9.
- Spotted Wing Drosophila (SWD). (n.d.). Retrieved from http://fruit.cornell.edu/spottedwing/
Serhat Solmaz is a MS student in the vanEngelsdorp Lab studying the effects of Nosema cerenae on honey bee pathophysiology at the University of Maryland.