Study Says One Neonicotinoid Insecticide Might Not Harm Honey Bee Colonies

As it can be easy to surmise at this point, the rising loss of honey bee colonies throughout the U.S. and the world is the result of multiple stressors, such as pesticides, habitat loss, climate change, malnutrition, viruses, and parasites, coming together in fatal combinations. Because of the seriousness surrounding the decline of honey bees, many governments and organizations have been performing studies in the hope of understanding the decline and presenting viable solutions to combat it. Recently, the Genetic Literacy Project (GLP) extended its study on how honey bees are affected by oilseed rape seeds treated with clothianidin, a neonicotinoid insecticide.

With this extension, GLP had another year of new data on honey bee colony development, mortality, pathogens, immune gene expression, and swarming. This is after they published a field study in 2015 on the effects of clothianidin on honey bees, solitary bees, and bumblebees. The new data on honey bees is from the experiment’s second consecutive year, and it was intended to help uncover the accumulative effects of clothianidin-treated fields on honey bees over a two-year period.

This data also features analyses on honey bee samples for several pathogens, symbiotic gut bacteria, and levels of immune gene expression. By GLP’s calculations, many parameters proved to be unaffected by clothianidin treatment, but the impact they did find was also said to be “mostly positive” in terms of side effects. Apparently, the placement of bee colonies at or near clothianidin-treated fields saw increased brood production for the experiment’s second year as well as more adult honey bees during both years.

GLP believes this offers insight regarding interactions between pesticides and pathogens, given they feel it demonstrates how foraging for oilseed rape treated with clothianidin had no visible negative consequences on honey bees at the colony level when it came to immune gene expression, microbial composition, and varroa mite infestations in field conditions. There is an acknowledgment by GLP that detrimental side effects may exist on an individual level for honey bees, but hive-level regulatory mechanisms seem to compensate for it.

This means that bee colonies with a strong, general health may be able to fight off the effects of clothianidin while less healthy colonies may succumb to the effects of the insecticide. From GLP’s perspective, these results seem to suggest that honey bee colonies as a whole are fairly robust at fighting off clothianidin in real-life agricultural landscapes, with the pressures of natural, moderate disease.