Drosophila suzukii (Matsumura), the Spotted Wing Drosophila (SWD), is native to Southeast Asia and rapidly invaded America and Europe in the past 20 years. SWD is a crop pest of soft-skinned fruits with a wide range of host plants, threatening the fruit industry worldwide and causing enormous economic losses. One step to control this invasive pest ... species is to understand its population dynamics and structure. In this work, I present the population genetics and development of SWD in Germany from 2017-2019 using microsatellite markers over eleven different sample sites. It is the first study that examines the genetic changes in SWD populations over three years compared to multiple international SWD laboratory strains. It was shown that SWD populations in Germany are highly homogenous. Differences between populations or years were not observed, indicating that populations are well adapted, migrate freely, and potential reinvasions from outside Germany either do not take place or are negligible. The results of this work help to understand SWD biology and population development. The high genetic variability and migration between populations could allow for a fast establishment of this pest species. This is especially problematic concerning the ongoing spread of this invasive species and could bear a potential for developing pesticide resistance. This could have a significant effect on pest control strategies for SWD in the future.