Entomopathogenic fungi are vital components of integrated pest management; however, environmental temperature is one of the key factors that limits their individual-level virulence, population-level transmission dynamics, and field efficacy. In this study, we isolated an indigenous fungal strain from a naturally infected Zeugodacus cucurbitae cadaver, and evaluated its biological characteristics, virulence, and horizontal transmission efficiency against Z. cucurbitae across 20–35 °C. A temperature-driven Susceptible–Infected–Removed (SIR) epidemiological model was developed to simulate infection dynamics and predict its epizootic potential. Morphological and molecular (ITS) analyses identified the isolate as Beauveria bassiana, designated as strain WZS5. WZS5 exhibited notable thermotolerance. At 30 °C, the strain displayed a short median germination time (7.7 h), high sporulation yield (1.1 × 108 conidia mL−1), and fast radial growth (4.8 mm d−1). Additionally, it showed substantial virulence with a median lethal concentration (LC50) of 1.32 × 107 conidia mL−1 and a median lethal time (LT50) of 5.28 days at a concentration of 1.0 × 108 conidia mL−1. Baseline biological activity was maintained even at 35 °C. At 30 °C, horizontal transmission was effective, yielding a cadaver sporulation rate of approximately 70.0%, a 4.0-day sporulation lag, and viable F1 conidia (88.6% germination). The SIR model adequately captured these dynamics (r = 0.919), predicting potential epizootic spread at 30 °C with a basic reproduction number (R0) of 1.90. This predictive framework quantifies temperature thresholds for fungal epizootics, providing valuable ecological insights for managing Z. cucurbitae in tropical and subtropical regions.
Fu et al. (Tue,) studied this question.