Effects of herbicide-tolerant transgenic oilseed rape genotypes on honey bees and other pollinating insects under field conditions

Field experiments were carried out to compare the diversity and density of pollinators foraging on two winter oilseed rape varieties, 'Falcon' and 'Artus', and their respective transgenic counterparts 'Falcon pat' and 'Artus LL', which are tolerant to glufosinate, a non-specific herbicide. The number of insects per 1000 available flowers was counted for the four main pollinators: honeybees, bumblebees, solitary bees, and Diptera. Additionally, on 'Falcon'/'Falcon pat' the foraging behaviour of the main pollinating insects, i.e., honeybees and bumblebees, was observed (number of flowers visited per min, foraging postures, intervariety flights). A pleiotropic effect could affect nectar and pollen production, therefore we measured nectar volume, nectar sugar concentration, and composition for the four plant genotypes, and on 'Falcon' and 'Falcon pat' pollen production was also estimated. The diversity and density of the foraging insect population observed on the transgenic genotypes were similar to that on the non-transgenic controls. Moreover, the foraging behaviour strategy was similar on 'Falcon' and 'Falcon pat', and honeybees flew indifferently across these two genotypes. No difference was found in nectar and pollen between the genotypes. Thus, we may assume that the insects do not discriminate between conventional and transgenic oilseed rape specifically resistant to glufosinate. A case-by-case approach is recommended for other genetic modifications to plants potentially visited by bees.