The demise of bumblebees: Linking pesticides and pathogens to declining populations

Study links use of specific pesticide to bumblebee pathogens associated with range contractions and population declines

Data resources used via GBIF : 67,725 species occurrences
Bombus pensylvanicus
American bumble bee (Bombus pensylvanicus) by Kathy Richardson via iNaturalist. Photo licensed under CC BY-NC 4.0.

Efficient pollinators of wild flowering plants and crops, bumblebees provide important ecosystem services, threatened by range contractions and declining populations. In the US, this has been linked to a variety of factors including urbanization, pesticides and pathogens.

In a study of bumblebees in the US, authors attempt to elucidate the relative importance of different stressors associated with range contractions. At 284 sites, they sampled and identified Bombus species, while screening for pathogens and quantifying landscape and pesticide usage.

Combining the field data with GBIF-mediated occurrences of eight target species, the authors used a machine learning model technique to show that the usage of the fungicide chlorothalonil was the best predictor of prevalence of the bumblebee pathogen Nosema bombi in four declining species. They also found that total fungicide usage was correlated with range contractions in all declining species.

Adding to existing evidence, this study highlights fungicide exposure–linked to pathogen prevalence–as a critical factor affecting threatened and endangered bumblebees in the US.

Link to original article

McArt SH, Urbanowicz C, McCoshum S, Irwin RE and Adler LS (2017) Landscape predictors of pathogen prevalence and range contractions in US bumblebees. Proceedings of the Royal Society B: Biological Sciences. The Royal Society 284(1867): 20172181. Available at: