Over the last decade, Drosophila suzukii Matsumura, an invasive pest of soft-skinned fruits, gradually established itself in Europe, often resulting in significant economic losses. In 2011, when D. suzukii was first described for Germany, the Julius Kühn Institut (JKI) started a monitoring program in southwest Germany to study the occurrence and activity of the fly. Capture data from late 2011–early 2018 from 100 traps were analyzed for the effect of weather and immediate habitat on trap captures at different times of the year. We identified five phases in the annual population development cycle of D. suzukii. We found that the mild winter of 2013/2014 helped the thorough establishment of D. suzukii in Germany. Habitat types in the immediate vicinity of the trap and local weather conditions had a strong influence on trap captures. Forest borders and hedges were found to provide adequate overwintering shelter for the flies. Trap captures in forests and hedges were generally higher than those of vineyards and orchards, even during the fruiting seasons. Summer capture rates were correlated with the number of heat days and precipitation. We also discuss briefly the limitations of using trap captures as representative of fly density in the field.

Drosophila suzukii is a globally invasive pest causing substantial losses in soft fruit production systems. While diel activity has been studied under laboratory conditions, long-term high-resolution field data remain scarce. Here, we present a multi-year automated monitoring dataset from four field sites in South-West Germany (2017–2019) using traps sampling at 3-hour intervals, combined with high-resolution environmental data. Across the study period, D. suzukii exhibited strong seasonal dynamics, with low activity in winter and early spring, increasing in late spring and summer, and declining in autumn. Diel activity patterns were not constant but varied with seasonal abundance and environmental conditions. During periods of high activity, captures were concentrated in daylight hours and often showed bimodal peaks in the morning and late afternoon. In contrast, during low-abundance periods, diel patterns were weak or absent. Temperature effects on capture rates were season-dependent, showing positive associations in late spring and autumn but negative associations in summer. Rain consistently reduced capture rates across all seasons, whereas wind showed weaker and less consistent effects. Overall, our results show that diel activity of D. suzukii emerges under specific seasonal and environmental conditions rather than being a fixed behavioural trait. The custom-built automated trapping system proved reliable for high-frequency field monitoring and provides a scalable approach for other small insect monitoring systems. These findings emphasise the importance of considering both temporal resolution and environmental context when interpreting trap data and designing pest management strategies.