While studying environmental factors that may possibly contribute to bumblebee population declines, a team of researchers from Cornell University found that fungicides might have an impact, though they were previously thought to be benign for bees.

Residue from fungicides used to control plant pathogens in crops are picked up by bees foraging for pollen and nectar. This in itself is not inherently harmful to the bees, but it is thought that the fungicide's interaction with insecticides might increase the toxicity. In particular, the researchers focused on the fungicide chlorothalonil, sold under the names Bravo, Echo, and Daconil, and commonly used on crops including peanuts and potatoes. Chlorothalonil has been linked to Nosema, a fatal gut infection in bees, as well as stunted colony growth.

Fungicides were also found to contribute to a decrease in the range of the bumblebees studied.

The scientists will continue to investigate the link between insecticides and fungicides as well as fungicide-pathogen interactions to determine the best use of fungicides to protect bees.

The study was funded by the USDA and the National Science Foundation. It can be purchased at https://tinyurl.com/ybsadeha.