Medicinal value of sunflower pollen against bee pathogens

Jonathan J Giacomini,Jessica Leslie,Rebecca E Irwin,Lynn S Adler,Evan C Palmer-Young,David R Tarpy

doi:10.1038/s41598-018-32681-y

Jonathan J Giacomini, Jessica Leslie + Show 4 more

Open Access

https://doi.org/10.1038/s41598-018-32681-y

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Abstract

Global declines in pollinators, including bees, can have major consequences for ecosystem services. Bees are dominant pollinators, making it imperative to mitigate declines. Pathogens are strongly implicated in the decline of native and honey bees. Diet affects bee immune responses, suggesting the potential for floral resources to provide natural resistance to pathogens. We discovered that sunflower (Helianthus annuus) pollen dramatically and consistently reduced a protozoan pathogen (Crithidia bombi) infection in bumble bees (Bombus impatiens) and also reduced a microsporidian pathogen (Nosema ceranae) of the European honey bee (Apis mellifera), indicating the potential for broad anti-parasitic effects. In a field survey, bumble bees from farms with more sunflower area had lower Crithidia infection rates. Given consistent effects of sunflower in reducing pathogens, planting sunflower in agroecosystems and native habitat may provide a simple solution to reduce disease and improve the health of economically and ecologically important pollinators.

Highlights

Pollinators are critically important for the preservation of plant biodiversity, and provide billions of dollars in crop pollination annually[1,2]
We focused on three monofloral pollens commonly grown in large monocultures in agroecosystems and visited by bees: rape (Brassica campestris), sunflower (Helianthus annuus), and buckwheat (Fagopyrum cymosum), as well as a mixed diet composed of the three monofloral pollens
Sunflower pollen significantly reduced Crithidia infection in bumble bees compared to all other pollen diets (χ2(3) = 111.2, P < 0.001)

Summary

Introduction

Pollinators are critically important for the preservation of plant biodiversity, and provide billions of dollars in crop pollination annually[1,2]. Many studies have examined the role of landscape factors, including plant diversity, on pollinator abundance and colony growth[6,7,8,9], but the role of particular plant species in mediating bee-pathogen dynamics is largely unknown. A recent study that incorporated a range of landscape factors and pesticide use data found that use of the fungicide chlorothalonil was the best predictor of the pathogen Nosema in four declining bumble bee species[9], but this work did not consider the role of particular plant species or pollen quality. Previous work has shown that nectar chemistry can mediate bee disease[20], and one study found that pollen from different plant species affects honey bee tolerance of the pathogen Nosema ceranae and expression of immune genes[21]. Field experiments suggest that Nosema infection can cause a rapid collapse of otherwise healthy colonies[27]

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