Bee natural history traits affect pollinator sensitivity to imidacloprid insecticide

Authors: Sampson, Blair; GREGORC, ALES - University Of Maribor, Slovenia; ALBURAKI, MOHAMED - University Of Southern Mississippi; Werle, Christopher; KARIM, SHAHID - University Of Southern Mississippi; Adamczyk, John; KNIGHT, PATRICIA - Mississippi State University

Submitted to: Proceedings of the Royal Society. B. Biological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2023
Publication Date: 5/3/2023
Citation: Blair Sampson , Aleš Gregorc , Mohamed Alburaki, Christopher Werle, Shahid Karim, John Adamczyk, Patricia Knight. 2023. Sensitivity to imidacloprid insecticide varies among some social and solitary bee species of agricultural value. PLOS ONE. https://doi.org/10.1371/journal.pone.0285167
DOI: https://doi.org/10.1371/journal.pone.0285167

Interpretive Summary: Bioassays were designed to test the health effects of sublethal concentrations of a neonic insecticide (imidacloprid) on honey bees and wild native bees. Bee species represented abundant pollinators of fruit and vegetable crops as well as of many wild plants. Bees displayed no visible tremors, except for small sweat bees. Adults sweat bees, honey bees, bumble bees and rose-mallow bees lived the longest, ~10 to 12 days, which indicated that body size does not reliably determine a bee's sensitivity to this insecticide. Imidacloprid equally reduced lifespans of male and female bees, except in the rose-mallow bee, whose aggressive, territorial males displayed longevities that were 4 days shorter than those of females, perhaps because of greater stress. All bee species became paralyzed sooner with increasing concentration. Among social bee species, bumble bees were particularly susceptible to paralysis. A higher sensitivity of solitary oligolectic bees to imidacloprid could diminish their nesting success as well as their impact on crop yield.

Technical Abstract: Bioassays using Apis and wild non-Apis species with differing natural histories tested the health effects of sublethal concentrations of imidacloprid on bee longevity and paralysis. Species were chosen for their high abundance and differences in sociality, floral specialization, age, and sex. Throughout the year, adult Apis mellifera and 11 species of wild bees were collected from flowering Vaccinium (blueberry), Cucurbita (squash and pumpkin), Helianthus (sunflower), and Abelmoschus (okra). In the laboratory, absorbent dental wicks presented bees with 0, 5, 20, and 100 ppb imidacloprid in 27% (1.25M) sucrose solution. Bees displayed no visible tremors, except for Halictis ligatus, which exhibited brief convulsions and only at 100 ppb imidacloprid. Imidacloprid shortened the lifespans of all tested solitary bees. Adults of H. ligatus, Apis mellifera, Bombus 2 spp., and Ptilothrix bombiformis lived the longest, ~10 to 12 days, which inferred susceptibility to imidacloprid can be independent of body size. Imidacloprid equally reduced lifespans of both sexes of bees, except in Ptilothrix bombiformis, a species with aggressive, territorial males whose longevity perhaps diminishes further with imidacloprid-induced stress. All bee species became paralyzed sooner with increasing concentration. Among the generalist (polylectic) social species tested, bumble bees were the most susceptible to paralysis. In conclusion, bee tolerance to imidacloprid based on mean longevity and paralysis rate was highest in Apis followed by Xenoglossa, Halictus, Trachusa, Ptilothrix, Melissodes 2 spp., Bombus 2spp., Habropoda, Svastra, and Peponapis. Higher sensitivities of solitary oligolectic bees to imidacloprid could diminish yields of crops that serve as these bees’ principal floral hosts.