Effect of non-nutritive sugars to decrease the survivorship of spotted wing drosophila, Drosophila suzukii

Authors: Choi, Man-Yeon; TANG, SIEW - Oregon State University; AHN, SEUNG-JOON - Oregon State University; AMARASEKARE, KAUSHALYA - Oregon State University; SHEARER, PETER - Oregon State University; Lee, Jana

Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2017
Publication Date: 4/5/2017
Citation: Choi, M.Y., Tang, S.B., Ahn, S., Amarasekare, K.G., Shearer, P.W., Lee, J.C. 2017. Effect of non-nutritive sugars to decrease the survivorship of spotted wing drosophila, Drosophila suzukii. Journal of Insect Physiology. 99:86-94. doi: 10.1016/j.jinsphys.2017.04.001.

Interpretive Summary: Spotted wing drosophila (SWD), Drosophila suzukii, is a severe invasive pest attacking a wide range a wide range of small fruits including almost all cherry cultivars. SWD exhibits a broad range of almost all varieties of small fruits including blackberries, blueberries, cherries, peaches, raspberries, strawberries, and grapes. Since the first outbreak in the U.S. in 2008, the distribution of SWD has been rapidly expanding across the U.S., Canada and Europe. The estimated economic impact from crop yield loss, drop in market value, and higher management cost is hundreds of millions of dollars in the U.S. alone, and increasing every year. To replace or reduce the use of chemical insecticides, alternative options are currently being developed, but there are still many critical gaps to be implemented against SWD in field. Scientists from USDA-ARS and Oregon State University in Corvallis, OR studied the effects of non-nutritive sugars erythritol and erythrose on the mortality of spotted wing drosophila, Drosophila suzukii, and discovered erythritol and erythrose as potentially toxic and having insecticidal activity to the fly. In a dose-dependent test, erythritol and erythrose significantly reduced fly longevity, with 100% mortality in all doses after feeding for 7 days. With a serial combination of sugar and erythritol solutions, the fly mortality was significantly increased for the same period. Also, the higher dose of erythritol regardless of the sucrose dose combined showed in greater mortality. This discovery emphasizes the potential of using non-nutritive sugars as an insecticide alone or combined with conventional or biological insecticides to enhance efficacy. While the present research focuses on D. suzukii, it can be expanded to other Dipteran pests.

Technical Abstract: In this study, we investigated the effects of non-nutritive sugars and sugar alcohols on the survivorship of spotted wing drosophila, Drosophila suzukii, and found erythritol and erythrose as potentially toxic to the fly. In a dose-dependent study, erythritol and erythrose significantly reduced fly longevity, with 100% mortality with 1, 0.5, 0.1 & 0.05M doses after feeding for 7 days. When sugar solutions were provided separately to flies for 7 days, there was no effect on survivorship regardless of erythritol concentrations. However, with a serial combination of sugar and erythritol solutions, fly survivorship was significantly decreased for the same period. Also, the higher dose of erythritol regardless of the sucrose dose combined showed in greater mortality. In a no-choice assay, D. suzukii ingested more erythritol than sucrose or water, indicating the fly continuously fed on erythritol for 72 hours. Also under no-choice conditions, erythritol and sucrose-fed flies gained more weight than water-fed flies. However, in two-choice assays, the amount of erythritol ingested was less than sucrose or water. Total sugar and glycogen levels among erythritol and erythrose-fed flies were significantly less than mannitol, sorbitol, xylitol, and sucrose-fed flies after 48 hours. This indicates that these two non-nutritive sugars can’t be used a substrate for enzymes involved in sugar metabolism. Although the metabolism of erythritol and erythrose is unknown in insects, the mortality of D. suzukii flies ingesting these sugars might be caused by two potential physiological changes. The fly is starved by feeding of non-metabolizable erythritol and erythrose, or experiences abnormally high osmotic pressure in the hemolymph with erythritol molecules diffused from the midgut. Non-nutritive sugars might be used as an insecticide alone or combined with conventional or biological insecticides to enhance efficacy. If other sugar sources are present, a palatable sugar might be mixed with erythritol to elicit feeding.