Assessing oviposition deterrence of spotted-wing drosophila by VOC dispensers fabricated from polyethylene tubing

Drosophila suzukii, commonly known as the spotted-wing drosophila (SWD) is a fruit fly that is native to southeast Asia and has caused significant economic losses to diverse fruit crops around the world. In this study, we evaluated certain naturally occurring volatile organic compounds (VOCs) that may serve as oviposition deterrents against SWD. Laboratory assays were conducted in environmental chambers with lab-reared SWD and blueberries as oviposition substrate. Four benzyl esters were assessed for their capacity to deter oviposition by constructing dispensers out of polyethylene tubing and felt. Two environmental chambers were used simultaneously, one for control and the other for the treatment, maintained at the same rearing conditions. Within each chamber, two mesh cages each contained three store-bought blueberries. A repellent dispenser containing 500 uL of compound was placed between the cages. For controls, an empty dispenser packet was used. 30 SWD individuals, 1:1 male:female, were released into the cages and given 24 hours to oviposit. Oviposition was quantified by inspecting each blueberry under a dissection scope to tally the occurrence of breathing tubes which extend from SWD eggs through the fruit skin. The release rate of the repellent dispensers was also quantified on a daily basis. We found that the strongest oviposition deterrent was methyl benzoate, a floral volatile that has been reported as an effective natural pesticide against SWD eggs and larvae. This compound also had the fastest release rate of the compounds assessed.