Distribution and seasonal dynamics of two distinct sex pheromone types in <i>Cnaphalocrocis medinalis</i> moths across China

Abstract BACKGROUND Cnaphalocrocis medinalis, a major migratory rice pest in Asia, shows significant variation in female sex pheromone composition across geographical regions. This study investigated the distribution and seasonal dynamics of two distinct sex pheromone strains in populations across China to improve monitoring accuracy and understand migration patterns. RESULTS Chemical analysis identified two pheromone types: an aldehyde‐alcohol blend (AA) dominated by Z13‐18:Ald (4.30 ± 2.68 ng per female), and an acetate ester blend (AE) dominated by Z11‐16:Ac (5.04 ± 0.72 ng per female). Among 339 females examined, the AE strain was substantially more prevalent (80–97%) in most regions. Ovarian development ranged from levels 2 to 4, with mating frequencies of 0–5 times, indicating the prevalence of the AE strain in natural populations. Large‐scale pheromone trapping monitoring across 106 sites outlined distinct geographical and seasonal distributions in males. Southern regions exhibited higher AE proportions in July–August, whereas northern areas, particularly the middle–lower Yangtze provinces, were dominated by the AA strain in August–September, often accounting for 60–90% of captures. For example, AA was &gt;90% in Nantong, whereas AE remained at &gt;80% in Jingzhou. Seasonal shifts occurred in some southern locations, such as Chongzuo, where AE surpassed AA by September. CONCLUSION Two pheromone strains of C. medinalis co‐occur across China with geographically and seasonally structured distributions. The AE strain predominates overall, but both strains must be used concurrently for accurate population monitoring. This pheromone polymorphism is likely to reflect different geographical origins of migratory populations and provides a foundation for region‐specific pest management strategies. © 2026 Society of Chemical Industry.