Effect of temperature on growth and development of rice weevil [ <i>Sitophilus oryzae</i> (L.) (Coleoptera: Curculionidae)] on polished rice

Abstract Rice weevils ( Sitophilus oryzae ), a major storage pest, cause both qualitative and quantitative losses of stored grains. Normally, chemical insecticide along with fumigation is practiced for the management, but it creates health hazards. So, this study investigates the effects of temperature and duration of exposure on rice weevils. Completely randomized design with two factors—factor (A) eight treatments: T 1 = −80°C, T 2 = −20°C, T 3 = 4°C, T 4 = 20°C, T 5 = 25°C, T 6 = 35°C, T 7 = 40°C, and T 8 = 50°C; factor (B) three durations of exposure—was carried out with three replications at laboratory condition of Entomology Division at Bangladesh Rice Research Institute from October 2023 to November 2024. The mortality percentage varied significantly across temperature and hours exposure time (HET), with 100% mortality observed at extreme temperatures (−80°C, −20°C, and 50°C) at 24, 48, and 72 HET. At moderate temperatures (20°C, 25°C, and 35°C), mortality was negligible to moderate (0%–11.67% at 24 HET and 48 HET), but increasing with prolonged exposure time (48.33% at 72 HET). Although 100% weevil mortality was achieved at 40°C, it required slightly extended durations (48 and 72 HET) for the 100% mortality. The F 1 adult emergence was highest (124.67) at 25°C, indicating optimal thermal conditions for rice weevil reproduction and development, while extreme temperatures completely inhibited adult emergence. The developmental period was shortest at 25°C and prolonged at 4°C, reflecting the metabolic slowdown at lower temperatures. There were no F 1 adults emerged at extreme temperatures (−80°C, −20°C, and 50°C), highlighting lethality of these thermal conditions. Weight loss of grains was highest at 20°C, 25°C, and 35°C due to active feeding and breeding, and highest number of F 1 adults emerged, while the minimal occurred at extreme temperatures. Low (&lt;4°C) and high (&gt;35°C) temperatures were particularly effective with prolonged exposure time for developing temperature‐based management practice. Weevil biology is influence by temperature, with low prolonging development but increasing mortality, moderate optimizing survival, increasing weight loss, and high reducing survival through biological stress.