README.R_Scripts from Pollen from multiple sunflower cultivars and species reduces a common bumblebee gut pathogen

Pathogens are one of the factors driving pollinator declines. Diet can play an important role in mediating pollinator health and resistance to pathogens. Sunflower pollen (<i>Helianthus annuus</i>) dramatically reduced a gut pathogen (<i>Crithidia bombi</i>) of <i>Bombus impatiens</i> previously, but the breadth of this effect was unknown. We tested whether pollen from nine <i>H. annuus</i> cultivars, four wild <i>H. annuus</i> populations, <i>H. petiolarus, H. argophyllus</i> and two <i>Solidago</i> spp., reduced <i>Crithidia</i> in <i>B. impatiens</i> compared to mixed wildflower pollen and buckwheat pollen (<i>Fagopyrum esculentum</i>) as controls. We also compared hand- and honeybee-collected pollen (which contains nectar) to assess whether diet effects on pathogens were due to pollen or nectar. All <i>Helianthus</i> and <i>Solidago</i> pollen reduced <i>Crithidia</i> by 20–40-fold compared to buckwheat pollen, and all but three taxa reduced <i>Crithidia</i> compared to wildflower pollen. We found no consistent differences between hand- and bee-collected pollen, suggesting that pollen alone can reduce <i>Crithidia</i> infection. Our results indicate an important role of pollen diet for bee health and potentially broad options within the Asteraceae for pollinator plantings to manage bee disease.