Overwintering Life History and Flight Performance of Mythimna separata (Walker, 1865) on Perennial Rice (Oryza sativa L.)

In Guangxi, China, winter ratoon tissues of perennial rice provide overwintering habitats for the migratory crop pest Mythimna separata (Walker, 1865) (Lepidoptera: Noctuidae). To understand the overwintering potential and fitness of this pest in perennial rice cropping systems, we evaluated the life history, population parameters, and flight performance of M. separata cohorts initiated in November, December, January, and February using group rearing and age-stage, two-sex life tables. The November cohort showed the highest intrinsic rate of increase (rm = 0.1009 d−1), while the February cohort exhibited the greatest fecundity (752.88 eggs/female) and flight capacity (7.61 h of flight during the 12 h flight period). In contrast, prolonged exposure to deep-winter cold severely suppressed survival, reproduction, population growth, and adult flight performance. These findings demonstrate that overwintering success depends strongly on the timing of cold exposure: gradual autumn cooling and late-winter warming can support population persistence, whereas sustained deep-winter cold is associated with reduced fitness. Perennial rice ratoon tissues may therefore facilitate pest carry-over between cropping cycles, and the overlap between spring ratoon regrowth and reproduction of late-winter cohorts may increase the risk of early-season outbreaks. Monitoring overwintering cohort dynamics together with ratoon phenology could improve early warning and support timely management of M. separata in perennial rice systems.