Entomopathogenic fungi can cause infectious diseases within host insect populations, while insects may counteract disease transmission through the strategy of isolating infected individuals. This study develops a system of differential equations to model the temporal dynamics of susceptible and infected individuals, as well as the concentration of fungal spores in the environment, to investigate the complex dynamics of disease transmission. The study focuses on three critical parameters: infection probability, population size, and isolation rate. The results show that infection probability is a key determinant of disease spread; as infection probability increases, the basic reproduction number (R_0) rises, potentially leading to periodic oscillations in disease incidence, highlighting the nonlinear response of disease transmission to changes in virulence. This underscores the importance of managing environmental factors such as temperature and humidity, which influence infection probability, to control disease spread. Furthermore, the analysis reveals that larger populations, due to higher contact frequency, exhibit more pronounced and persistent disease dynamics, suggesting that population density control is an effective strategy for managing disease outbreaks. The study also identifies isolation behavior as crucial for disease control, where moderate increases in isolation rates can lead to complete eradication under certain conditions. The timing of spore production relative to host death is also identified as a key variable affecting the efficacy of isolation. In conclusion, this study elucidates the complex interplay between infection probability, population size, and isolation behavior, providing a theoretical basis for optimizing biological control strategies using entomopathogenic fungi and managing high-density insect populations.