Impacts of microsporidia on development, survivorship, and immune responses in the blue orchard bee (Osmia lignaria Say, Hymenoptera: Megachilidae)

Microsporidia are obligate intracellular parasites found in various animal hosts. Most notably, microsporidians that infect insects include species described in the genera Nosema and Vairimorpha. Most microsporidia species studied in insects have become a significant issue in managed insects such as silkworms and honey bees. Few studies detail microsporidia presence in native solitary bee populations in the United States, and fewer publications have investigated how virulent and infectious microsporidia is to solitary bees in the genus Osmia. In a recent investigation, we detected Vairmorpha ceranae in diapausing adults of wild-caught O. lignaria, indicating an active infection persisting from larval to adult development. Additionally, a higher prevalence of infection was found at a study site with higher failed nest cells. To investigate how microsporidia impact O. lignaria, we employed an in vitro assay to monitor how different concentrations of spores affect O. lignaria when fed to larvae. Significantly lower survival was found in bees fed the higher levels of spores. We are determining how the infections by microsporidia interact with other stressors and impact development, survivorship, and immune response in O. lignaria.