To cope with the shortage of wild bees, many growers of fruit such as strawberries, use ‘managed pollinators’ – either honeybee hives or specially bought-in commercial bumblebee colonies – to help pollinate their crops. However, often the commercial bumblebees don’t leave the nest, or they become distracted by wildflowers growing nearby and end up avoiding the crop flowers.
NRI’s Dr Sarah Arnold, who led a team of pollinator experts from NRI, working together with Dr Michelle Fountain’s team from NIAB EMR (a horticultural research centre in Kent), think they may have found a solution to this problem.
Data from previous studies had shown that honeybees fed on caffeine formed longer-lasting memories of odours associated with good food – meaning that they were better at recalling flying routes and the best sources of nectar.
In this study, funded by the Biotechnology and Biological Sciences Research Council (BBSRC), Biobest (who supply bumble bees to fruit farms) and Berry Gardens Ltd. (a fruit growers’ production and marketing group), the team wanted to discover whether bees could be primed to target specific odours. Could inexperienced bumblebees (Bombus terrestris audax) consistently locate new food sources that were emitting a learned floral odour, if they had been trained with the caffeine cocktail before leaving the nest?
Drs Arnold and Fountain concocted a special composition of caffeine, sugar and the specific target flower smells that they wanted their bees to find, and wafted the blend through the nest before releasing the bees in the laboratory where robotic flowers awaited them.
The researchers, including postdoctoral researcher Dr Jan Dudenh̦ffer, arranged the laboratory setup so half of the flowers had the target odour Рa replica of the odour of strawberry flowers Рand the other half had a different odour, linalool, a common flower scent that is not present in strawberry flowers.
“In our laboratory experiment”, Dr Arnold explains, “we found that the bees we had trained using the caffeine/sugar/odour priming treatment were much more interested in the target flowers with the strawberry odour, compared to the distractor flowers.”
Using the team’s new caffeine-odour priming method on crops could boost fruit yields because the bees are more focused on visiting and pollinating the crop flowers. It could also reduce competition with wild bees for wildflowers by keeping the managed bees around the crop – one of several environmental benefits. Flowering strawberry plants grown on a farm may automatically then be visited by more bees, as when the bees leave the nest, they’re particularly primed and ‘zoned in’ to find certain flowers.
“We can help guide that behaviour and enhance their performance in the field”, explains Dr Arnold, “by giving them a little bit of priming or pre-training within the nest. This can have implications in farming, and it gives us insights into how bees think and learn, so it tells us a bit about how caffeine works in their brains.”
Dr Arnold says that previous experiments on giving bees caffeine to alter their behaviour depended on putting the caffeine directly onto the flowers to attract them – rather impractical on a large scale. This new experiment contains the special blend within the nest and the scientists can control how much caffeine the bees are exposed to.
“It’s like a person drinking coffee while revising for an exam. We generally know how coffee helps us concentrate and stay focussed, as well as helping us remember complex information better, and what our limit is. We’ve shown that caffeine increases the bees’ enthusiasm and activity generally and it makes the memory formation stronger. The bees that did have caffeine showed more interest in the target odour flowers compared to the ones that did not.”
“Fascinatingly, it shows that there are commonalities in the neurobiology between us and bees. Bees have got a brain the size of a grass seed and a very short life span compared to us, but can still accomplish complex tasks.”
Dr Arnold’s team is hoping to benefit growers of fruit crops like strawberries, and help them to get more value for money out of the commercial bumblebee colonies that they buy to pollinate the crops. Using this caffeine blend method means that commercial bees can be delivered to growers ‘crop ready’ and more likely to pollinate the target crop without competing with wild bees for nectar from wildflowers.
Field trials were carried out with NRI’s collaborators, NIAB EMR, led by Dr Michelle Fountain, using commercial bumblebee colonies and real strawberries, indicating it can also work in the field.
