Effects of clothianidin in a prairie restoration: Bee foraging and floral resource abundance

Clothianidin—a neonicotinoid pesticide—has been shown to impair behaviors related to foraging abilities of bees (Hymenoptera: Apoidea), which could have broader effects on the plants that rely on these insects for reproduction. As part of a large-scale prairie restoration field study, a small dose (92.5mg) mimicking non-target drift of clothianidin was applied to six blocks of eight 20 by 20-meter plots, annually since 2019, to be compared to 6 control blocks. Forb characteristics (flower abundance transects, ground cover quadrats) and counts of foraging bees were measured three times a year between June and August, along with end-of-season biomass.
For our most-visited flowers (twelve genera each representing 1% or more of the total bees captured), clothianidin-treated plots had more inflorescences, despite lower ground cover and biomass of forbs in general. However, no differences were observed between treatments for the number of foraging bees, suggesting that despite greater flower abundance in clothianidin treatments, bees may prefer flowers in clothianidin-free environments. Further research into how clothianidin may impact growth and reproductive effort of different forb groups could explain the unexpected trends observed in forb characteristics.