All spots on Drosophila: from basic to applied research to support IPM in soft and stone fruits

Abstract: From the late 2000s on Drosophila suzukii (also known as Spotted Wing Drosophila, SWD), native to Southeast Asia, invaded the European and American continent, and rapidly became a key pest of soft and stone fruits. This serious economically damaging pest forced fruit growers to adopt calendar-based sprays with (broad-spectrum) insecticides, disrupting integrated pest management (IPM) programs. Over the past decade, we conducted in-depth research on ways to improve monitoring and IPM control strategies for SWD. In this journey, we uncovered fundamental insights on basic research and translated them through applied research into improving IPM strategies in the field. Laboratory olfactometer experiments revealed that the preference between fermentation and fruit volatiles is strongly determined by the physiological status of the flies, with summer morph females relatively more attracted to fruit odours. Consequently, peripheral factors such as the timing in the season and type and phenology of the fruit crop play an important role in the trapping efficacy for monitoring as well as mass trapping purposes. In order to evaluate and model the interaction with trapping devices, fluorescent powders to mark D. suzukii flies yielded a clearly detectable and highly persistent mark, without any adverse effects on the survival and behaviour of the flies in mark–(release)–recapture studies. Using the knowledge and research techniques acquired, the bait and trap design of SWD traps was significantly improved throughout the studies. In addition, a decision support model was developed, which integrates a weather-driven phenological prediction model to the knowledge of the optimal action of different crop protection products against SWD. The efficiency of the latter as further enhanced by research findings from both lab and field studies concerning bait spraying applications. Finally, in order to make monitoring practice feasible for growers we developed an automatic monitoring system for SWD. This automatic monitoring system is based on an optical sensor capable of identifying SWD by measuring its wingbeat characteristics. We demonstrated that using this sensor D. suzukii can be identified while entering a monitoring trap, and effectively be distinguished from the common (unharmful) fruit fly Drosophila melanogaster.