Improving honey bee tolerance to pathogen infection by optimizing macronutrients within artificial diets

With the ever-increasing demand for pollination services of agricultural operations, honey bees (Apis mellifera) are oftentimes nutritionally stressed and at an increased risk of coming into contact and becoming infected with pathogens than they would naturally. It has been shown that the health of honey bees infected with pathogens can be improved by ensuring proper nutrition. However, commercially available pollen substitutes vary widely in their macronutrient protein (P) to lipid (L) ratios, and it is unknown what target ratio can help bees better deal with pathogen infection. The purpose of this study was to determine what protein (P) to lipid (L) ratio within artificial diets have a positive impact on the survivorship, physiology, and overall health of honey bees infected with either of two common honey bee pathogens: Nosema sp. and Deformed wing virus (DWV). We conducted cage assays where both infected and non-infected cohorts of bees were fed one of four diet treatments: a high P: low L diet (40P:10L), a low P: high L diet (20P:30L), an intermediate diet ratio at which non-infected honey bee colonies self-select for in the field (30P:20L), or no diet whatsoever. Differences in diet consumption, survivorship, pathogen load, and physiology were compared between the different infection groups fed our diets with varying macronutrient ratios. The purpose of this study is to identify at what macronutrient ratio honey bees can better tolerate infection with pathogens in order to better tailor commercially available pollen substitutes for managed colonies on altered and changing landscapes.