Exploitation of population dynamics and chemical communication for integrated management of Drosophila suzukii

Drosophila suzukii (Matsumura), also known as Spotted Wing Drosophila (SWD), is a vinegar fly belonging to the Diptera order and Drosophilidae family. It is native to South East Asia and it has recently invaded western countries, threating fruits production. Because of its rapid spread, the economic impact has been huge in most of the invaded countries. D. suzukii infestations generate direct and indirect economic impacts. For this reason, deeper information about the biology, ecology, chemical-ecology, genetics and behavior are necessary to better manage the species. This thesis was developed to contribute towards a better understanding of these topics, in order to find a scientifically supported and effective solution. In particular, this work focused on four aspects: 1) analyze the genetic structure of different Italian populations, 2) understand the spread and therefore the capacity of movement of D. suzukii in large and small scale, 3) study the oviposition behavior with an in depth characterization of the chemical volatiles involved in the substrate choice and 4) manipulate the egg-lay behavior thanks to an innovative lure, which can work as an alternative oviposition substrate. In the first chapter, we characterized the genetic structure of the invasive species D. suzukii in Italy. Our analysis showed extensive genetic homogeneity among D. suzukii collected in Italy. The relatively isolated Sicilian population suggests a largely human-mediated migration pattern while the warm climate in this region allows the production of soft fruit, and the associated D. suzukii reproductive season occurring much earlier than on the rest of the peninsula. Understanding seasonal and daily migrations D. suzukii populations is fundamental, since it could help farmers and industries decide where to apply specific management techniques. This was the aim of the third and fourth chapter. Furthermore, the finding of a consistent seasonal and daily movement from the crop to the surrounding vegetation and towards areas with different altitude, may lead to use treatments, especially chemical, in precise periods of the year and in defined zones on the border of the crop. The fifth chapter was focused on the oviposition behaviour of D. suzukii. The goal of this work was to elucidate behavioural and chemical aspects of short-range site selection of this species. In particular experiments evidenced the release of an anal secretion over the fruit surface near the oviposition site, which seems to have an attractant function. The knowledge gained with this study may accelerate establishment of control strategies based on the interference and disruption of the D. suzukii communication during the oviposition processes. Finally, the main target of my sixth chapter had more practical purposes focusing on the identification of new attractants for D. suzukii able to interfere with its movement and, consequently, with the potential to be used as baits for pest monitoring and control. This project, carried out at the Oregon State University, led to the development of new gum matrix as a potential sink for D. suzukii eggs in a commercial-standard cropping system. Taken together, the results presented in this thesis highly contribute to enhancing our understanding of D. suzukii biology, ecology and chemical and to expand integrated pest management option.