Guest Contributor

**Ayana Harscoet**
Bowdoin ‘21

Bumblebee on sunflower. Photo by Ronda Ryan

When you’re a bumblebee, there’s no CVS-type-one-stop-shop to take care of all your pathogen-related issues. But fortunately for these pollinators, certain food sources have the potential to mitigate infections. This week’s paper, published in Ecological Entomology and led by George Locascio, a professor at UMass Amherst, finds that consuming sunflower pollen can effectively reduce infections of a bumblebee gut pathogen, Crithida bombi, in the bumblebee Bombus impatiens.

Understanding disease dynamics can help us figure out how to combat certain stressors contributing to species decline in pollinators, a necessary endeavor given the crucial role that these organisms play in global ecosystems and food systems. Locascio et al. conducted two experiments to investigate the relationship between sunflower pollen and pathogen transmission, hoping to get at the effects of specific factors like duration and timing of pollen exposure.

In their first experiment, which they refer to as “exposure during foraging,” the authors wanted to see whether sunflower pollen affected the transmission of C. bombi. Would bees be at higher risk of infection if they visited inoculated flowers without pollen versus flowers with pollen? As it turns out, the presence of sunflower pollen had no effect on the pathogen at this point in the infection process—bees were similarly infected regardless of whether they visited flowers with or without pollen.

The second experiment focused on post-infection—could a bumblebee recover from infection with the right diet? Yes! But sunflower pollen isn’t an immediate cure: bumblebees recovered much better when they were consistently consuming sunflower pollen for 7 days after infection than for just 3.5 days. And timing also mattered—if they started consuming sunflower pollen 3.5 days after infection as opposed to immediately after, the pollen didn’t combat the infection as effectively. That said, bumblebees consuming sunflower pollen for 7 days beginning a week after infection still had relatively good recovery rates. So, as Locascio et al. conclude, the effectiveness of sunflower pollen is dependent on both how soon a bumblebee consumes it after infection, coupled with the amount or duration of consumption. For best results, a bumblebee would consistently consume sunflower pollen for at least a week immediately after infection.

That said, sunflower pollen is no nutritious food source for bumblebees—it lacks sufficient amino acid richness and has even been suggested to reduce bee development and growth. Much like we wouldn’t last long on a diet of prescription meds, it’s important for bees to consume pollen from a variety of flowers to receive both adequate nutrition and pathogen defenses.

Ayana Harscoet

Bowdoin ‘21

Doris Duke Conservation Scholar

Jones Lab Student Researcher