New research from the University of Oxford has revealed that bumblebees cannot taste pesticides present in nectar, even at lethal concentrations. This means bumblebees are not able to avoid contaminated nectar, putting them at high risk of pesticide exposure and posing a threat to crop pollination. The research has been published in Life.
Bumblebees play one of the most important roles on the planet, pollinating many of our crops. Plus, they can be very cute. Sadly though, our favorite flying fluffballs are also under threat whilst they work; a new study has discovered that bumblebees are unable to detect even lethal concentrations of pesticides in nectar, putting both their health and crop pollination at risk.
A good sense of taste isn’t unusual for bees – they are known for being able to differentiate between sweet, salty, and bitter flavors. It’s this adeptness that researchers from the University of Oxford focused on, wanting to investigate if it could enable the bees to detect pesticide-contaminated nectar, which is generally thought of as tasting bitter, and avoid it.
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. First, they used electrophysiology to record the responses of neurons in taste sensilla (i.e., ‘tastebuds’) on the 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 behavior by offering them either pure sugar solutions or pesticide-laced sugar solutions to feed on.
The results 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 behavior 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.
Lead author Dr Rachel Parkinson (Department of Biology, University of Oxford), said: ‘As bumblebees cannot taste pesticides and don’t experience immediate negative consequences from drinking them, they likely would not be able to avoid consuming nectar contaminated with pesticides in the field.’
Although bees did not drink less of the pesticide-laced solutions, the authors demonstrated “bitter” taste avoidance using the compound quinine. Quinine in sugar solution was a deterrent to bees at high concentrations. At low concentrations, bees were observed to ingest less of the sugar solution, however, the amount of time they spent in contact with the feeding solution was the same.
