Susceptibility of cranberries to Drosophila suzukii (Diptera: Drosophilidae)

Authors: Steffan, Shawn; Lee, Jana; SINGLETON, MERRITT - University Of Wisconsin; VILAIRE, AURIEL - Washington State University; WALSH, DOUG - Washington State University; LAVINE, LAURA - Washington State University; PATTEN, KIM - Washington State University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2013
Publication Date: 12/20/2013
Publication URL: http://handle.nal.usda.gov/10113/58299
Citation: Steffan, S.A., Lee, J.C., Singleton, M., Vilaire, A., Walsh, D., Lavine, L., Patten, K. 2013. Susceptibility of cranberries to Drosophila suzukii (Diptera: Drosophilidae). Journal of Economic Entomology. 106(6):2424-2427.

Interpretive Summary: The spotted-wing drosophila (SWD) is rapidly expanding across the US, infesting fields, orchards, and vineyards in all major fruit growing regions. In some cases, crop damage has been devastating, particularly within the small-fruit category. While cranberries have not suffered any crop losses attributable to SWD, there has been concern within the cranberry industry as to whether cranberries might serve as a host for SWD. No studies existed that specifically addressed this question, so we screened ripe, under-ripe, and over-ripe cranberries for their susceptibility to SWD. We also assessed the effect of wounded fruit on the potential for infestation. Our work reveals that undamaged fruit of any developmental stage are not suitable hosts for SWD—only fruit that has been wounded and is in a state of decay may be exploited by SWD. Current-year undamaged cranberries, therefore, are relatively safe from SWD infestation. We show that SWD females do not perceive cranberries to be a viable host substrate, and that larvae cannot survive in undamaged, non-decaying fruit. The fact that damaged, decaying fruit can support SWD larval development suggests that cranberries may contribute to regional source-sink dynamics with SWD populations. Large numbers of previous-year cranberries decay every spring and summer in Wisconsin cranberry marshes, potentially generating large numbers of SWD that could infest other crops.

Technical Abstract: Drosophila suzukii Mastsumura (Diptera: Drosophilidae), commonly referred to as the spotted-wing drosophila, is an exotic species that has proven a troublesome pest of fruit production in the U.S. The fly targets small fruit and thus represents a concern for the U.S. cranberry industry. Two studies were conducted to assess whether cranberries may serve as hosts for D. suzukii. In the first study, the suitability of ripe, unripe, and over-ripe cranberries were assayed by examining oviposition and larval development in no-choice trials. In a second study, wounded and unwounded fruit were examined as potential hosts in choice trials. The first study showed that ripe, unripe, and over-ripe cranberries were unsuitable hosts (very few eggs were laid, with no surviving larvae). In the wounded/unwounded berry trials, no larvae survived to adulthood among unwounded berries. Among wounded fruit, however, adult flies emerged. Together, these results suggest that unwounded cranberries—even previous-year fruit—are unsuitable as hosts for D. suzukii. Conversely, wounded ripe fruit can serve as hosts. Fortunately for cranberry growers, wounded fruit tend to rot and wilt in the field, so are unlikely to be harvested. Across the landscape, cranberry marshes may contribute to regional source-sink dynamics.