Population dynamics of Drosophila suzukii across elevations in Wenchuan, China

Drosophila suzukii is a devastating global pest of soft-skinned fruits, yet its population dynamics in mountainous agricultural systems where cultivation extends across elevational gradients remain poorly understood. To address this gap, we conducted 2 years of intensive monitoring (2023-2024) in sweet cherry (Prunus avium) orchards at three elevations (1360-1910 m) in Wenchuan, China, characterizing adult population fluctuations and fruit infestation patterns. Adult population peaks were progressively delayed with increasing elevation, closely tracking local cherry phenology. Generalized linear mixed models revealed that adult abundance was positively associated with mean temperature and fruit maturity, with temperature effects strengthening significantly at higher elevations. Despite the later population buildup, infestation incidence at the highest site (1910 m) reached the 40% infestation threshold at a fruit maturity ratio 0.459 lower than at the lowest site (1360 m), indicating heightened susceptibility of high-elevation orchards. Field surveys identified 11 non-crop host species supporting D. suzukii reproduction before sweet cherry maturation. Notably, early-ripening Lonicera standishii at high elevations and Prunus pseudocerasus at low elevations served as critical population reservoirs. Interplanting with P. pseudocerasus advanced both the seasonal arrival of D. suzukii and the onset of sweet cherry damage by 5-10 d. These findings demonstrate that elevational gradients create asynchronous pest pressure, with high-elevation orchards facing disproportionately rapid infestation despite cooler temperatures. We provide an empirical basis for elevation-specific monitoring and management strategies such as the sterile insect technique, emphasizing targeted early-season intervention in non-crop hosts to mitigate spillover into commercial plantings.