Bees are important pollinators of agricultural crops, but this can expose them to pesticides while they collect nectar and pollen -- some of which are very toxic to bees. Bees are known to be adept at tasting and differentiating sugary solutions. Certain toxic compounds, like quinine, taste "bitter" to bees, so the researchers sought to find out whether this sense of taste could help them avoid drinking pesticides.

The researchers used two methods to test whether bumblebees (Bombus terrestris) could taste neonicotinoid and sulfoximine pesticides in nectar which mimicked that of oilseed rape (Brassica napus), and if they would avoid drinking pesticides over a very broad range of concentrations. They used electrophysiology to record the responses of neurons in taste sensilla (i.e., 'tastebuds') on bumblebee's mouthparts. This allowed them to track how often neurons 'fired' and therefore the strength of response to the taste. The researchers also tested the bumblebees' feeding behaviour by offering them either sugar solutions or pesticide-laced sugar solutions to feed on.

The researches demonstrated that the responses of the neurons were the same whether the bees drank sugar solution or sugar-containing pesticides. This indicates that the bumblebees' mouthparts do not have mechanisms to detect and avoid common pesticides in nectar. In the behaviour experiments, the bees consumed the same amount of food, regardless of whether the solution contained pesticides or not. This was even the case when the pesticides were present at concentrations high enough to make the bees very ill. The findings are important because they show that bumblebees cannot avoid pesticide exposure using their sense of taste.