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Bumble Bee Queens Slower to Start Colonies After Neonic Exposure

Bombus impatiens queen
Bumble bee queens, such as the Bombus impatiens queen shown above, forage in the spring as they initiate new colonies. New research shows that exposure to small amounts of the neonicotinoid insecticide imidacloprid during that period can delay a B. impatiens queen’s nest initiation and brood emergence—if the queen survives the exposure at all. (Photo credit: Flickr/USGS Bee Inventory and Monitoring Lab)
Spring is an important period for bumble bees, as that’s when new colonies get their start. When a solitary bumble bee queen emerges from hibernation, she initiates a nest and then does the foraging work herself, until her first offspring hatch, develop into workers, and relieve her from all duties but egg laying. Thus, should any harm befall the queen in this early period, it can have ripple effects on the health of the developing colony.
According to a new study published last week in Environmental Entomology, queens of the bumble bee species Bombus impatiens that encounter the neonicotinoid insecticide imidacloprid in that foraging period show delayed nest initiation and brood emergence—if they survive the exposure at all.
Researchers at the University of Minnesota conducted an experiment in which they exposed B. impatiens queens to imidacloprid at levels between 1 and 25 parts per billion (ppb) in a sugar syrup, to “reflect a typical flower bloom period during which bees may become exposed to neonicotinoids when foraging on contaminated nectar and pollen in the environment.” They then measured how many queens survived, how long they took to start a nest, and how many eggs they laid.
Queens treated with the insecticide at 1, 10, and 25 ppb died in greater numbers, and sooner, compared to untreated queens (though no significant difference was found at the 5 ppb treatment level). Meanwhile, though untreated queens began laying eggs between 13 and 20 days after the experiment began, queens exposed to imidacloprid were slower to begin their nests, some taking several weeks longer, “which suggests a possible dose-dependent delay and recovery by queens once exposure ended,” according to the authors of the study, Judy Wu-Smart, Ph.D., a doctoral candidate at the University of Minnesota at the time of the study and now an assistant professor and extension specialist at the University of Nebraska-Lincoln, and Marla Spivak, Ph.D., distinguished McKnight professor at Minnesota.

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