Floral nectar helps to control parasites in bumblebees.

Plants produce molecules called secondary metabolites that are harmful to herbivores but in some cases can also protect animals from parasites. To see whether such metabolites in nectar similarly affect pollinators, Leif Richardson at Dartmouth College in Hanover, New Hampshire, and his team infected eastern bumblebees (Bombus impatiens) with an intestinal parasite and gave the bees one of eight different nectar compounds. Four of the metabolites reduced the load of parasites by 60–80%.

The compound with the strongest effect on parasites, anabasine, did not seem to boost bumblebee survival, but the team says that these chemicals in nectar could benefit the bee colony as a whole by reducing parasite spread.

Proc. R. Soc. B 282, 20142471 (2015)