Cheng Li

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 (r_m = 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.

Cyrtorhinus lividipennis, a key natural enemy of the brown planthopper, Nilaparvata lugens, has been observed to tolerate short-term high-temperature exposure; however, the physiological and molecular mechanisms underlying this heat tolerance remain unclear, which may hinder its effective conservation and utilization. Here, we combined physiological and biochemical assays with transcriptome sequencing to elucidate the physiological and molecular mechanisms of heat tolerance in C. lividipennis following 1 h exposure to three temperatures: 26 °C (control), 33 °C (moderate heat stress), and 40 °C (severe heat stress). At 40 °C, sorbitol, trehalose, lipid, and glycogen contents increased significantly, whereas glycerol levels declined. Transcriptomic profiling revealed temperature-dependent DEGs enriched in starch and sucrose metabolism, galactose metabolism, glycerolipid metabolism, oxidative phosphorylation, and protein folding, sorting, and degradation, with pronounced temperature-dependent upregulation of heat shock protein (HSP) gene families. Together, these results demonstrate that C. lividipennis coordinates its heat stress response through soluble polyol accumulation, which is known to act as a compatible osmolytes that help stabilize proteins and membranes and mitigate thermal damage, energy metabolic reprogramming, and HSP-mediated proteostasis, thereby providing a theoretical basis for its conservation and utilization in sustainable paddy agroecosystems.

The predatory function and numerical responses of natural enemy insects are critical for evaluating their biological control potential, particularly in understanding pest suppression mechanisms and ecological adaptability. Here, we examined the predation capacity of Tytthus chinensis Stål (Hemiptera: Miridae) on Sogatella furcifera eggs under laboratory conditions (24 ± 1 °C, 12:12 h light:dark photoperiod, 75% humidity). Functional response experiments were conducted at different prey densities (3, 4, 10, 20, and 30 eggs/day), and life table parameters were established to evaluate the effects of prey density on the development, reproduction, and population dynamics of T. chinensis. The daily average predation of nymphs significantly increased with age, and their functional responses fitted the Holling Type II response. In the adult stage, the daily average predation of females was significantly higher than that of males, and males had a higher a/T_h ratio, which reflected sex-specific predation strategies. Prey density significantly influenced survival, reproduction, and population dynamics. The minimum prey density required for population stability was 4 eggs/day, and survival and reproduction rates markedly increased at 10 eggs/day. At 30 eggs/day, females reproduced earlier, and the lifespan of males was shortened. These findings confirm the strong pest control ability of T. chinensis and highlight the critical role of S. furcifera egg density in regulating the population dynamics of T. chinensis.