Monthly Dynamics of Nosema canburensis Infection on Graphosoma italicum Müller (Hemiptera: Pentatomidae) Populations

Microsporidia are obligate intracellular parasites that predominantly cause chronic infections in their hosts, relying entirely on host cells for development and reproduction. Among entomopathogenic microsporidia, climatic variables such as temperature and humidity are pivotal in influencing infection dynamics. This study focuses on Nosema canburensis, a microsporidian pathogen of the Italian striped bug, Graphosoma italicum, a pest species that adversely affects Apiaceae crops. Field studies conducted between June and September from 2022 to 2024 in Trabzon Province, Türkiye, documented the prevalence of N. canburensis within populations of G. italicum. Microscopic analyses identified infection rates, with Ortahisar district showing significantly higher prevalence (16.67%) compared to Beşikdüzü (0%). Microscopic findings were supported by molecular confirmation via SSU rRNA-based PCR. The highest infection rate (22.5%) was recorded in 2023, while the lowest was observed in 2022 (13.33%). Seasonal fluctuations revealed peak infection rates in July and the lowest in September, consistently over three years. Statistical analyses indicated a significant positive correlation between temperature and microsporidiosis prevalence (r = 0.462, P < 0.05) and a weak negative correlation with humidity (r = -0.077, P > 0.05). The findings highlight the critical role of climatic factors in shaping microsporidiosis outbreaks and emphasize the potential of N. canburensis as a natural regulatory factor in pest insect management. Future research should focus on elucidating the environmental and biological interactions influencing the epidemiology of entomopathogenic microsporidia.