Effects of sulfoxaflor on caste development in the common eastern bumblebee (Bombus impatiens)

Successful crop production depends on agrochemicals to control pests. However,
agrochemicals can have negative consequences on beneficial insect pollinators, such as
bees. We investigated the effects of an emerging pesticide, sulfoxaflor, on the common
eastern bumblebee, Bombus impatiens. We performed a series of both acute and chronic
toxicity tests in replicated microcolonies to determine how sulfoxaflor affected the
viability, behavior, and physiology of B. impatiens. Interestingly, we found that B. impatiens
workers had an apparent preference for sulfoxaflor-contaminated sugar syrup over sugar
syrup alone. We also found that workers and drones were more sensitive to sulfoxaflor
than queens. Our results showed that chronic exposure to sublethal concentrations of
sulfoxaflor significantly reduced the number of honey pots, egg batches, and amount of
sugar syrup consumed in microcolonies. Notably, the observed changes in the
reproductive abilities of bees exposed to sulfoxaflor were caused by impeding ovary
development and reducing egg laying. Surprisingly, we found that chronic sulfoxaflor
exposure did not affect crawling velocity, time spent moving, distance traveled, or head
movement frequency at any concentration. Ongoing experiments in queenright colonies
aim to investigate how chronic sulfoxaflor exposure may affect the timing of reproductive
caste development, sex ratios, tissue-specific gene expression, and phenotypic variation
among offspring. Overall, this investigation provides novel information on how sulfoxaflor
may impact caste development of an important native pollinator at field realistic
concentrations.