Priming bumble bees with caffeine, odour of the target crop, and a food reward, has minimal effects on fruit crop pollination and yield in a semi-commercial setup

by Arnold et al.

Caffeine is produced in the nectar of some plants including coffee and citrus. When honeybees feed on caffeinated nectar, it improves their memory for scents associated with food.  Caffeinated bees might therefore pollinate more effectively as they can more effectively relocate a nutritious flower while at the same time transferring pollen.  We have previously shown in the laboratory, using artificial flowers, that bumblebees exposed to a floral scent in the nest seek out that scent outside the nest when foraging for food, if they consumed caffeine while learning the scent. 

Here we report a semi-field experiment (using individual enclosed polytunnels) in which we tested whether bumblebees could be “primed” to visit strawberry crop flowers more by learning to recall a strawberry flower scent alongside caffeinated sugar-water in the nest before being released. If the commercial bumblebees formed a strong memory for strawberry flower scent, paired with a good food experience in the nest, we expected that they would already have a preference for the crop flowers compared to any other flowers when foraging. 

However, when this was tested in 12m long mini-polytunnels, there was no consistent difference between bumblebees that had received caffeine or not, and whether the artificial strawberry floral odour was present in the nest or not. There was also no consistent difference in strawberry fruit size or quality between tunnels containing control bees, caffeine-primed bees, and bees that received the odour-sugar combination in the nest but no caffeine, meaning that caffeine and floral odour did not make these bees better pollinators.

Read the scientific article in JPE