Drosophila suzukii flight performance reduced by starvation but not affected by humidity

Authors: WONG, JESSICA - Oregon State University; CAVE, ADAM - Department Of Veterans Affairs; LIGHTLE, DANIELLE - University Of California Agriculture And Natural Resources (UCANR); Mahaffee, Walter - Walt; Naranjo, Steven; WIMAN, NIK - Oregon State University; WOLTZ, MEGAN - Lindenwood University; Lee, Jana

Submitted to: Journal of Pest Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2018
Publication Date: 7/4/2018
Citation: Wong, J., Cave, A., Lightle, D., Mahaffee, W.F., Naranjo, S.E., Wiman, N., Woltz, M., Lee, J.C. 2018. Drosophila suzukii flight performance reduced by starvation but not affected by humidity. Journal of Pest Science. 91(4):1269-1278. https://doi.org/10.1007/s10340-018-1013-x.
DOI: https://doi.org/10.1007/s10340-018-1013-x

Interpretive Summary: Spotted wing drosophila (SWD) is a worldwide pest of berries and small fruits. The surrounding environment and availability of food affect the physiological status of SWD. The physiological health of SWD could also affect their ability to fly. One way to study flight is to tether an insect on a flight mill, the insect flies in circles, and the speed and rotations are tracked electronically. While this is not natural flight, it is a convenient way to compare insects from different experimental groups. In this study, two experiments compared the effects of diet and humidity on SWD flight performance, and a third experiment compared the lipid, glycogen and sugar levels of flown and un-flown flies to determine the energetic requirements for flight. Overall, SWD females flew about 27.16 m (median) for 2.37 min at 0.18 m/s. The female that flew the farthest flew 1.75 km for 2.35 h. SWD given either fruit blossoms, fruits, or standard lab diets flew farther distances and longer durations than starved flies. Humidity did not alter flight of starved or fruit-provisioned SWD. Interestingly, flies provided blossoms flew farther and longer in low and high humidity conditions compared to moderate humidity conditions. The observed trend is not explainable in this study. Lastly, it remains unclear whether SWD use lipids, glycogen, sugar, or another energy source for flight because tethered individuals may not have flown enough to deplete energy reserves.

Technical Abstract: Drosophila suzukii is widely studied because of its status as a global pest of berries and soft fruits. Environmental conditions and access to food resources impact the physiology and fitness of D. suzukii; these factors could also affect dispersal. Flight mills are a convenient tool for measuring and comparing the flight performance of insects. In this study, two experiments compared the effects of diet and humidity on D. suzukii flight performance using custom-built flight mills, and a third experiment compared the nutrient reserves of D. suzukii flown or not flown on flight mills. Overall, the median flight distance was 27.16 m, the median flight duration was 2.37 min, and the mean flight velocity was 0.18 m/s. The maximum distance flown was 1.75 km and the maximum flight duration was 2.35 h. Drosophila suzukii provisioned with blossoms, fruits, or standard lab diets flew farther distances and longer durations than starved flies. Humidity did not affect flight performance of starved or fruit-provisioned D. suzukii. Interestingly, flies provided blossoms flew farther and longer in low and high humidity conditions compared to moderate humidity conditions. The observed trend is not explainable in this study, nor is it explicit evidence that humidity influences D. suzukii flight performance. It remains unclear whether D. suzukii use lipids, glycogen, sugar, or another energy source for flight because tethered individuals may not have flown enough to deplete energy reserves. This study provides a foundation for future research on D. suzukii dispersal.