Toxicity Profiling Validates Trajectory Modeling for Identifying Sogatella furcifera Migration Sources in Southern China

<i>Sogatella furcifera</i> (Horváth) is a major migratory rice pest, yet accurate source attribution for this insect remains a persistent challenge. To assess the accuracy of trajectory modeling in determining the source areas of <i>S</i>. <i>furcifera</i>, we examined an early-season migration event into HN in May 2024. Backward trajectories were simulated from 15 sites in HN, and insecticide toxicity assays were conducted to determine LC₅₀ values for pymetrozine and nitenpyram in 26 field populations collected from HN and GX. Trajectory analyses indicated that northwestern HN populations were traced primarily to western GX and northern Vietnam, central HN populations to central/southern GX, western GD, and northern Vietnam, and southeastern HN populations to northeastern/southeastern GX and western GD. Critically, toxicity tests confirmed the trajectory predictions. In particular, no statistically significant differences in LC₅₀ values were detected between HN populations and their identified source areas for either insecticide, while significant differences occurred in comparisons with non-source regions for both insecticides. These findings demonstrate that combining trajectory modeling with toxicity testing effectively identifies <i>S</i>. <i>furcifera</i> source areas during early migration. This study confirms the utility of trajectory analyses and provides an actionable strategy for monitoring and early warning systems targeting migratory pests.