The microsporidium Nosema ceranae (a fungi) and the ectoparasite Varroa destructor (a mite) are common biotic stressors of honeybees that produce serious damages to the colonies. The parasitic cycle of V. destructor is composed of a phoretic and reproductive phase. During the latter, the parasite enters brood cells, reproduces and feeds on the hemolymph and fat bodies of bee pupae impinging on their immune system resulting in more frequent physical deformities in newborn bees. In addition, N. ceranae, a gut intracellular parasite, causes nosemosis, the most widespread disease of adult bees. As the main source of lipids and proteins in honey bees, pollen is a major nutrient involved in development and health since many studies have shown its role in shaping honeybee traits, especially immune competence and tolerance against pathogens and parasites. The aim of this project is to investigate the impact of pollen supplementation in adult honeybees exposed to Nosema and previously to Varroa at the larval stage. Impacts of Varroa parasitism in laboratory conditions will be investigated on bee larval growth and on the microbiome in emerging bees. Long term effects on these experimental bees will examine their tolerance and resistance against Nosema exposure both in lab and semi-field conditions. We will focus on the relationships existing between gene expressions, peptidome/proteome modulation and phenotypic traits. We will describe how biotic stressors effects are coupled to interactions between feeding behavior and the microbiota composition. Given our joint expertise, we propose a unique experimental design. This includes impact of nutrition at adult stage and its interaction with most common pathogens, Varroa and Nosema, in both laboratory and semi-field experiments in a simple 4-Tunnels disposition. This interdisciplinary project allows us to examine the effects of those stressors observed all along the beekeeping season.