Dietary consumption of the plant phytochemical, gelsemine, by worker honey bees (Apis mellifera) affects queen bee egg laying

Yellow or Carolina jasmine/jessamine (Gelsemium sempervirens) is a flowering plant that serves as a model for the study of plant-pollinator interactions. During the early spring, it produces abundant flowers that are visited by generalist pollinators, such as honey bees (Apis mellifera), especially when other floral resources are scarce. Beekeepers in the Southeastern USA have observed signs of hive intoxication and weakening when yellow jessamine is in bloom, posing implications for hive and apiary management. The phytochemical gelsemine, which is a toxic indole alkaloid present in the plant’s pollen and nectar, may be linked to these observations. Few studies have looked at the effects of ecologically relevant concentrations of gelsemine on honey bee health at the colony level and on queen fecundity. We used Queen Monitoring Cages (QMCs), microcolonies composed of a queen and a small number of workers maintained under laboratory conditions to primarily investigate the impact of gelsemine exposure on queen fecundity, with additional measurements taken for worker mortality, number of workers in the brood area, and consumption of food resources. We exposed the workers to gelsemine by adding it to sucrose solution using field-relevant concentrations that ranged from 20 to 200 ppm for up to 15 days. We found that queen fecundity was significantly reduced in two of four experiments. Overall, worker mortality was low. In addition, when workers consumed sucrose solution containing higher doses of gelsemine, evidence of an aversion effect was observed. This study highlights one facet of yellow jessamine’s potential impact on honey bee colony health and promotes additional research looking at the behavioral and physiological mechanisms contributing to these responses.