Like honeybees, bumblebees are dying off. Although many theories abound for the colony collapse disorder of honeybees, most don’t apply to bumblebees. For example, bumblebees are not subject to stress caused by long-distance transport, being fed sugar not honey, and the use of pesticides in the hive to control mites.
A major contributing factor to the decline of bumblebees appears to be the use of fungicides, chlorothalonil in particular. Chlorothalonil, which is sold under band names Bravo, Echo, and Daconil, is used on potatoes, tomatoes and other agricultural crops, as well as turfgrass. “This fungicide has been linked to reduced colony growth in Bombus impatiens [the common eastern bumble bee] and increased likelihood of Nosema ceranae infection in honeybees,” writes McArt et al (2017). N. ceranae is a parasite that affects bumblebees and honeybees.
As with colony collapse disorder, there is no single factor responsible for the bumblebee decline. In nature, no factor works alone. This creates a challenge to researchers but also makes the situation for bees even more dire. McArt et al (2017) state that “while most fungicides are relatively non-toxic to bees, many are known to interact synergistically with insecticides, greatly increasing their toxicity.”
Source: SH McArt, C Urbanowicz, S McCoshum, et al. Landscape predictors of pathogen prevalence and range contractions in US bumblebees. 2017. Proceedings of the Royal Society B. Volume 284. Issue 1867.
- Janet Wallace