Location: Southern Horticultural ResearchTitle: Environmental ethanol as an ecological constraint on dietary breadth of Spotted-Wing Drosophila, Drosophila suzukii Mat. (Diptera: Drosophilidae)
|STAFNE, ERIC - Mississippi State Extension Service|
|LARSON, DREW - US Department Of Agriculture (USDA)|
Submitted to: Acta Horticulturae
Publication Type: Proceedings
Publication Acceptance Date: 8/15/2015
Publication Date: 5/24/2016
Citation: B.J. Sampson, E.T. Stafne, D.A. Marshall-Shaw, S.J. Stringer, T. Mallette, C.T. Werle and D. Larson. 2016. Environmental ethanol as a reproductive constraint on spotted wing drosophila and implications for control in Rubus and other fruits. Acta Horticulturae 1133: 411-418.
Interpretive Summary: Spotted-wing Drosophila (SWD) is a highly destructive pest of American berry crops. Female flies lay their eggs below the thin skin of healthy intact berries. As a result, SWD flies do not breed in rotting tissue and so they do not have to feed on fermenting juices, which may contain toxic levels of ethanol. We therefore tested whether ethanol is harmful to SWD and if this natural compound can be used to control SWD populations in cultivated berries. We discovered that SWD flies were easily killed by ethanol when compared with a native fruit fly species. Ethanol concentrations >2.5%, by increasing adult mortality, reduced the size of SWD pupal and adult populations. Male SWD were more than 2 to 3 times more sensitive to ethanol than were females with sex ratios increasingly favoring females at higher concentrations. These results show that SWD are incapable of colonizing the habitat of native fruit flies and may be even controlled with ethanol as a palatable ingested insecticide.
Technical Abstract: Spotted-wing Drosophila (SWD), Drosophila suzukii, is a recent fruit pest of the Americas whose destructiveness stems from its subcutaneous insertion of eggs into cultivated berries via a female’s prominent double bladed and serrated ovipositor. Atypical of most other Drosophila, D. suzukii adults and larvae are non-saprophagous. Therefore, these flies do not have to contend with fermented substrates containing toxic levels of ethanol. Currently, we do not know if D. suzukii can safely ingest environmental ethanol, which could have important implications for host selection, reproductive potential, chemical control, and the need for crop sanitation. We designed a series a laboratory experiments to measure critical life history traits of D. suzukii feeding on Rubus and Vaccinium in an ethanolic environment. These life history traits included adult survivorship, sex ratio, and optimal reproductive output. D. suzukii were quite sensitive to ethanol when compared with D. melanogaster. Ethanol concentrations >2.5% reduced SWD pupal and adult production as well as increased adult mortality. Male SWD were more than 2 to 3 times more sensitive to ethanol than were females with sex ratios increasingly favoring females at higher concentrations. These results taken together suggest that little if any overlap between the niches of SWD and native D. melanogaster will prevent either species from displacing the other. In fact, SWD may create more habitat for wild Drosophila at the expense of both wild and cultivated fruit species.