Agri-environment nectar chemistry suppresses parasite social epidemiology in an important pollinator

Abstract

Emergent infectious diseases are a principal driver of biodiversity loss globally. The population and range declines of a suite of North American bumblebees, a group of important pollinators, have been linked to emergent infection with the microsporidian Nosema bombi. Previous work has shown that phytochemicals in pollen and nectar can negatively impact parasites in individual bumblebees, but how this relates to social epidemiology and by extension whether plants can be effectively used as disease management strategies remains unexplored. Here we show that caffeine, identified in the nectar of Sainfoin, a constituent of agri-environment schemes, significantly reduced N. bombi infection intensity in individual bumblebees and, for the first time, that such effects impact social epidemiology, with colonies reared from wild caught queens having lower prevalence and intensity of infection. Furthermore, infection prevalence was lower in foraging bumblebees from these colonies, suggesting a likely reduction in population-level transmission. Our results demonstrate that phytochemicals can impact pollinator disease epidemiology and that planting strategies, which increase floral abundance to support biodiversity could be co-opted as disease management strategies.

A neonicotinoid pesticide alters how nectar chemistry affects bees

“…Furthermore, across taxa, bees can vary in their ability to cope with NSMs, perhaps as a result of evolutionary history with specific plant taxa (Tiedeken et al, 2016). As interest grows in understanding the benefits of nectar and pollen secondary chemistry in agroecosystems (Adler et al, 2021;Folly et al, 2021;Fowler et al, 2020) or use in promoting pollination service (Arnold et al, 2021), our results suggest an important caveat, which is that systemic pesticides may alter these dynamics.…”

“…Caffeine, for example, in the nectar of plants such as Citrus, Coffea and Onobrychis (sainfoin) increases bee activity (e.g. Figure 2c), reduces parasite load (Folly et al, 2021) and promotes pollen transfer (Thomson et al, 2015). The addition of IMD, which B. impatiens workers do not show any preference for on its own (Muth et al, 2020), and which limits activity (Figure 2c,d), would likely result in lowered visitation rate with potential negative impacts on plant fitness.…”