Bauer B, Morawetz L, Ribarts A, Wüest R & Krenn HW. 2023.
Journal of Apicultural Research, DOI: 10.1080/00218839.2023.2277986 Link. Published online 29 November 2023

Abstract

High summer temperatures caused major crop losses in scarlet runner beans (Phaseolus coccineus) in Austrian agriculture. To evaluate the impact of temperature on pollination, a greenhouse experiment was conducted. Pollination of P. coccineus by Apis mellifera was studied under standard temperature conditions (22 °C) and was compared to heat stress conditions (35 °C) in the greenhouse as well as to natural insect–flower interactions in the field trial. Under heat stress conditions, workers of A. mellifera significantly decreased their flower visitation, while the duration of flower visits significantly increased compared to normal greenhouse temperatures. Heat stress leads to a foraging stop of honey bees on the flowers of runner beans within a few days. It is concluded that the raised ambient temperature that we are facing during global warming may have negative effects on pollination and fruit set of P. coccineus.