Honey bee foraging in spring oilseed rape crops under high ambient temperature conditions

Abstract

Honey bee foraging activity on the flowers of two spring rapeseed varieties ‘SW Savann’ and ‘Ural’ was evaluated. High air temperature throughout the study period allowed us to investigate the interaction between plants and their pollinators under weather conditions unusual for Lithuania. Analysis of flowering intensity and honey bee density in the two rape varieties showed that ‘Ural’ produced on average 4.6% more flowers than ‘SW Savann’, however, honey bee density in ‘Ural’ plots was about 4% lower than that in ‘SW Savann’ plots. A decrease in flowering intensity was followed by a decrease in honey bee density in both rape varieties. A strong increase in ambient temperature had a negative impact on the foraging of honey bees on flowering plants. The lowest honey bee density in the investigated rape plots was recorded in the afternoon, when air temperature reached +43°C. High ambient temperature affected oilseed rape flowering and pollinator density on flowers and this could have had a negative effect on seed yield of oilseed rape.