Researchers from the University of Göttingen and the University of Hohenheim, Germany, suggest that flower diversity may reduce the impact of insecticides on wild bees.
In a large-scale experimental study, researchers from the universities of Göttingen and Hohenheim, as well as the Julius Kühn Institute, have found that a higher flower diversity may mitigate the impact of insecticides on wild bees, as well as increasing their breeding success.
As published in the scientific journal Ecology Letters, the researchers investigated how successfully the wild bee Osmia bicornis (red mason bee) reproduced. The wild bees were experimentally kept in more than 50 large enclosure cages with flower mixtures of varying wild plant diversity and insecticide-treated oilseed rape. Subsequently, the reproductive success of the wild bees, as measured by the number of their brood cells and emerged offspring, was investigated over several months.
The effect of flower diversity on wild bees
The research team found that the number of cells that the wild bees created for their offspring where species-rich flowering mixtures were available was twice that of wild bees where only oilseed rape was available.
The reproductive success of the wild bees, which have to supply their offspring with pollen and nectar, increased both in cages with a large diversity of flowering plants, and where there were particularly important plant species. In contrast, if oilseed rape treated with clothianidin (from the neonicotinoid class of insecticides), was available to the bees, this had a negative effect on their reproductive success. However, the negative effect of the insecticide only occurred in cages with oilseed rape monocultures, which suggests that such effects can be mitigated by alternative food resources from species-rich flowering mixtures.
“One possible explanation is that bee larvae benefit from additional nutrients, and are exposed to fewer insecticides, when the pollen of other plant species besides oilseed rape is available to them,” explains Felix Klaus, first author of the study and PhD student in the Agroecology Group at Göttingen University.