Toxicity of erythritol, a sugar alcohol and food additive, to Drosophila suzukii (Matsumara)

Since its recent invasion in Europe (2008) Drosophila suzukii has been responsible for severe economic losses in small fruit, cherry and strawberry cultivation. Because of the short generation time and high fecondity it is likely that D. suzukii will become resistant to some of the most widely used pesticides like spinosad and lambda-cyhalothrin. The use of these toxic insecticides comes with health and safety issues for consumer and grower. Erythritol, a sugar alcohol and a food additive, is safe for human consumption, but was shown to be toxic to fruit flies (Drosophila melanogaster). In this study, we assessed the toxicity of erythritol to D. suzukii by feeding them four different media: sugar/erythritol, sugar/no-erythritol, no-sugar/erythritol and a no-sugar/no-erythritol medium, in a no-choice test. After two days, there was a clear decrease in the survival of adult flies being kept on the no-sugar/erythritol medium, after six days only 2% survived compared to: 100% survival at the sugar/no-erythritol medium, 62% survival at the no-sugar/no-erythritol medium and 82% survival at the sugar/erythritol medium. Erythritol clearly has a toxic effect on D. suzukii adults, although this effect is much lower when erythritol is combined with sugar as alternative carbohydrate source. The lower survival percentage on the no-sugar/no-erythritol medium can be explained by the lack of an energy source. We also assessed the dose effect of erythritol on egg laying, larval, pupal and adult development. The outcomes indicate a repellent effect of erythritol on egg laying behaviour, even if gravid D. suzukii females had no other option to deposit eggs. When the amount of erythritol in the medium reached 110 g L^-1 no eggs/larvae were able to develop into pupae. Our findings clearly demonstrate, for the first time, the toxicity of erythritol for different life stages of D. suzukii, although the effect was diminished in presence of an alternative carbohydrate source. Lab and field trials with fruits or fruit production sites treated with erythritol should bring more clearness about the insecticidal capabilities of erythritol for potential future crop protection strategies in commercial fruit growing.