Effect of erythritol on Drosophila suzukii (Diptera: Drosophilidae) in the presence of naturally-occurring sugar sources, and on the survival of Apis mellifera (Hymenoptera: Apidae)

Authors: Choi, Man-Yeon; LUCAS, H - Oregon State University; SAGILI, R - Oregon State University; Cha, Dong; Lee, Jana

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2018
Publication Date: 11/28/2018
Citation: Choi, M.Y., Lucas, H., Sagili, R., Cha, D.H., Lee, J.C. 2018. Effect of erythritol on Drosophila suzukii (Diptera: Drosophilidae) in the presence of naturally-occurring sugar sources, and on the survival of Apis mellifera (Hymenoptera: Apidae). Journal of Economic Entomology. 112(2):981-985. https://doi.org/10.1093/jee/toy362.
DOI: https://doi.org/10.1093/jee/toy362

Interpretive Summary: Spotted wing drosophila (SWD), Drosophila suzukii, is a global economic pest of small fruits. While chemical insecticides effectively control this fly, negative impacts are incurred on the environment and human health. While alternatives including biological and cultural controls are being researched, these approaches are still under development, requiring approval for release, or costly. Therefore, a non-toxic chemical compound would be feasible for growers. Scientists from USDA-ARS, and Oregon State University at Corvallis, OR studied effect of erythritol formulation on the mortality and fecundity of SWD with naturally-occurring sugar sources, and on the survival of honeybees. The study discovered the erythritol formulation combined with sucrose reduced the longevity of SWD regardless of the presence of wounded blueberries. Besides causing death, erythritol ingestion appears to interfere with the ovipositional behavior and/or physical process of egg laying. The formulation did not decrease survivorship of honeybees. From this study we suggest the erythritol formulation can be a potential insecticide used alone or as a delivery agent combined with conventional or biological insecticides to enhance their efficacy. While the present research focuses on SWD, this tool can be expanded to other fly pests.

Technical Abstract: Previous studies have demonstrated various non-nutritive erythritol sugar combinations having insecticidal effects on SWD in lab and greenhouse trials. Erythritol ingestion did not elevate the fly’s carbohydrate reserves, and was highly concentrated in the hemolymph and slowly excreted. These results suggest that mortality is likely caused by: 1) starvation from feeding on non-metabolizable erythritol; and 2) physiological imbalance with abnormal osmotic pressure increased in the hemolymph. While erythritol kills SWD in controlled environments, flies in the field might feed on naturally-occurring sugar sources. Therefore, our first study evaluated the impact on fly mortality in the presence of wounded fruits. The erythritol formulation, 2.0 M erythritol:0.5 M sucrose or sucrose- and erythritol-only controls was fed to flies with access to 0 – 60 % wounded blueberry fruits. Survival on the formulation was lowered with wounded fruit. Nevertheless, survival on the formulation was consistently lower than sucrose controls with/out wounded fruit. This suggests that the formulation still has a detrimental effect when competing sugar sources are present. While previous studies have found erythritol to reduce fecundity, this was confounded by flies dying in erythritol treatments. Thus, our second study examined the three diets on fecundity and egg load of live female SWD. Females laid fewer eggs on blueberries when fed erythritol-only or the formulation than sucrose. Unexpectedly, the number of ovarial eggs in flies fed the formulation was higher than sucrose-fed flies, suggesting that erythritol might inhibit SWD from laying eggs through a physiological imbalance. Lastly, erythritol is ideal being non-toxic to humans and lethal to SWD. But, this formulation may be toxic to honeybees whom might occasionally forage in post-bloom fields where are treated. Thus, we evaluated honeybee survivorship by enclosing bees with one of three diets in a cage. The formulation had no discernible impact on adult survivorship during a 7-day period.