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

Abstract

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 ( Helianthus annuus ) dramatically reduced a gut pathogen ( Crithidia bombi ) of Bombus impatiens previously, but the breadth of this effect was unknown. We tested whether pollen from nine H. annuus cultivars, four wild H. annuus populations, H. petiolarus, H. argophyllus and two Solidago spp., reduced Crithidia in B. impatiens compared to mixed wildflower pollen and buckwheat pollen ( Fagopyrum esculentum ) 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 Helianthus and Solidago pollen reduced Crithidia by 20–40-fold compared to buckwheat pollen, and all but three taxa reduced Crithidia compared to wildflower pollen. We found no consistent differences between hand- and bee-collected pollen, suggesting that pollen alone can reduce Crithidia 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.

Effect of timing and exposure of sunflower pollen on a common gut pathogen of bumble bees

“…Because previous studies indicate that multiple cultivars of sunflower and some relatives suppress C. bombi (LoCascio et al, 2019), future studies could directly supply bee colonies with sunflower pollen to see whether sunflower pollen supplements can benefit bees at the whole-colony level. Because previous studies indicate that multiple cultivars of sunflower and some relatives suppress C. bombi (LoCascio et al, 2019), future studies could directly supply bee colonies with sunflower pollen to see whether sunflower pollen supplements can benefit bees at the whole-colony level.…”

“…We used single pollen species comparisons because sunflower pollen and buckwheat pollen (both from Changge Hauding Wax Industry, Henan, China) have similar (low) protein and amino acid concentration , but consuming buckwheat pollen results in much higher C. bombi infection than consuming sunflower pollen (Giacomini et al, 2018;LoCascio et al, 2019). To evaluate how the duration and timing of sunflower pollen consumption after infection affected C. bombi counts, we inoculated individual worker bees from commercially available hives that were confirmed to be C. bombi-free via weekly subsamples of five bees.…”

Bumble bee parasite prevalence but not genetic diversity impacted by the invasive plant Impatiens glandulifera

“…, LoCascio et al. ). Such potential for floral resources to provide natural resistance to pathogens has been partly studied in bumble bees (Manson et al.…”

“…, LoCascio et al. ) and honey bees (Giacomini et al. ) but also in some solitary bee species (Spear et al.…”

“…In addition, among floral traits, the chemical composition of floral resources and especially secondary compounds has been shown to impact interactions between pollinators and their parasites by reducing parasite transmission (Richardson et al 2015) and parasite load (Manson et al 2010, Spear et al 2016, Giacomini et al 2018, LoCascio et al 2019. Such potential for floral resources to provide natural resistance to pathogens has been partly studied in bumble bees (Manson et al 2010, Giacomini et al 2018, LoCascio et al 2019 and honey bees (Giacomini et al 2018) but also in some solitary bee species (Spear et al 2016). Understanding how plant species affect parasite prevalence is important for the selection of plant species for mitigating strategy (e.g., composition of floral strips to support pollinators and optimize pollinator health) (Vaudo et al 2015).…”