Trade-offs between immunity and reproduction have been demonstrated in several insects, and are strongly dictated by nutrition. Bombus impatiens, or the common eastern bumblebee, is a widespread pollinator that forages on pollen from plants with different protein, lipid, and secondary metabolite profiles. One of its most common pathogens is Crithidia bombi, a trypanosomatid gut parasite whose infectivity is affected by host diet. Dandelion (Taraxacum officinale) pollen reduces Crithidia infection, but lacks many essential amino acids, making it a poor nutritional source. Red maple (Acer rubrum) pollen results in high infection, but is nutritious. Both pollen types are available during the critical time of colony establishment in the early spring. I first investigated the effects of different ratios of dandelion and red maple pollen on infection in B. impatiens workers and found that diets with higher proportions of dandelion pollen resulted in reduced concentrations of Crithidia cells in the hindgut. I then investigated the interactions between nutrition and infection on reproductive outcomes in bumblebee microcolonies. Using a 2x2 factorial design with diet and infection as the factors, I predicted that in bees fed the red maple-dominant diet, reproductive investment would be prioritized as an adaptation to a resource-rich environment. For the dandelion-dominant diet, immune upregulation would result in reduced infection at the cost of lower egg and larvae production. These results will add to our understanding of the effects of nutritional availability and pathogen spread on bee reproduction.