Survival of western bean cutworm, Striacosta albicosta (Smith), subjected to simulated overwintering temperature scenarios

The western bean cutworm (WBC), Striacosta albicosta (Smith), is an important pest of corn. It overwinters as a pre-pupa in the soil inside of an earthen chamber. This study aimed to investigate WBC pre-pupal survival under simulated diapause conditions using laboratory-controlled temperature regimes. WBC pre-pupa were placed individually in cups containing sand and randomly assigned to treatments (n = 1,000). Treatments included a control at constant 26°C for 119 days; warm diapause with 26°C (14 days), 5°C (21 days), and 26°C (84 days); cold diapause at 0°C (28 days), 5°C (7 days), and 26°C (84 days); oscillation diapause I alternating 5°C and 0°C every 7 days for 35 days, followed by 26°C (84 days); and oscillation diapause II doubling cold exposure times, then 26°C (84 days). Pre-pupae were individually monitored through weekly observations for survival and pupation; if pupation occurred, pupal sex, length, width, and weight, as well as emergence rate of adults were also recorded. Survival analysis was performed using the Kaplan-Meier method, and the log-rank test (χ² = 106.56, df = 4, p < 0.0001) indicated significant differences. Control and warm diapause treatments had the longest median survival, while cold and oscillation diapause treatments were significantly shorter, suggesting physiological stress. Desiccation was the main cause of mortality across treatments. Among morphological parameters, only pupal weight differed significantly between treatments. Thermal regimes simulating oscillating temperatures during overwintering reduced WBC survival, mainly due to desiccation stress, and may affect diapause success and adult emergence.