Abstract
AIMS: As a gastrotoxic biocontrol agent employed for locust outbreak management, the infectivity of Paranosema locustae demonstrates significant dependence on pre-ingestion environmental exposure conditions, particularly temperature fluctuations, humidity levels, and UV radiation intensity, making the systematic investigation of these abiotic factors crucial for optimal field application. METHODS AND RESULTS: In this study, we simulated key environmental parameters (temperature, humidity, and UV radiation) that critically influence P. locustae viability during the pre-infection phase of host exposure. Analyzed the locust growth curve post-infection, the pathogen's copy number, dormancy factor Lso2 gene expression, and phosphorylated protein levels. Results show a marked decline in lethality and infectivity of P. locustae after prolonged exposure to water, especially at 20°C for 15 days, the survival curve became similar to that of the negative control group. In contrast, drying at 40°C for 15 days preserved its pathogenicity. The pathogen exhibited strong UV resistance, remaining infectious after 24 h of UV exposure at intensities over 100 µW/cm². After 5-10 days of dry conditions, the significant increase in Lso2 gene expression highlights the entry of P. locustae into true dormancy, which subsequently returns to baseline with extended exposure. Western blot analysis supported that sustained phosphorylation is vital for P. locustae lethality. CONCLUSIONS: Paranosema locustae demonstrates high-temperature tolerance, with dry heat and UV exposure maintaining infectivity, while wet environments reduce its viability.