Vertical and temporal dispersal of Drosophila suzukii in the field

Spotted-wing drosophila (SWD) is a polyphagous, invasive vinegar fly that continues to be a significant economic concern to berry producers throughout the world. SWD rapidly expanded their range since its initial detection in the United States which could be due to seasonal, long-distance migration However, little is known about SWD aerial and seasonal dispersal. Previous studies investigating SWD flight behavior have focused on horizontal movement in a field and used baited traps, which could alter SWD movement. Therefore, we examined the vertical and temporal dispersal of SWD between sexes (females and males) before and after raspberry season, and with passive sampling. SWD adults were collected with clear sticky cards at five varying heights within and above raspberry canopy (1, 2, 4, 6 and 7.3 meters) in 2017, 2018, and 2019. Traps were setup in June or July and collected weekly until first snow fall (between late October and early November). There was a significant increase of SWD caught (female and male) in August and September and catch numbers decreased in October. Approximately 89% of the female and male SWDs were trapped within and slightly above the raspberry canopy (i.e., 1 and 2 meters). However, we did find SWD at altitudes of 4, 6, and 7.3 meters, which could be indication of patch-leaving or wind dispersal behavior. As SWD continues to be a detrimental pest, gaining implication on its seasonal long-dispersal behavior can improve IPM programs by incorporating a forecasting model or determining when SWD may infest or leave a field.