Pollinators in a pickle: Assessing bumble bee resilience to extreme weather under pesticide exposure in cucumber fields

Pesticide use is a major driver of pollinator declines. Insecticides, as well as herbicides and fungicides, can pose significant lethal and sublethal risks, including disrupting critical behaviors such as nursing and foraging. While these impacts are increasingly well-studied in controlled conditions, how behavioral disruptions lead to adverse outcomes in naturalistic environments is not well-understood. Recent studies have found that some formulations inhibit thermoregulatory capacity, thus pesticides may also exacerbate the effects of fluctuating and extreme temperatures caused by climate change.
We conducted a field experiment in seven cucumber farms using bumble bee (Bombus impatiens) colonies and computer vision-based automated tracking. At each site, we deployed three rounds of queenright colonies for approximately ten days, and captured within-nest and foraging behaviors of individually tagged bumble bees using overhead cameras in the nest box. We also collected wax and bee samples from each colony at the end of the deployment period, and screened them for a comprehensive suite of pesticide residues. Lastly, we captured temperature data using weather stations and in-nest sensors. Combining the resulting data on bee behavior, pesticide residue, and temperature, we evaluate the impacts of field-realistic exposure on: a) within-nest and foraging activity, and b) behavioral resilience to fluctuating and extreme temperatures. We predict lower bee activity and higher sensitivity to temperature extremes at sites with higher levels of pesticide toxicity.
This work advances our understanding of pollinator health and pollination services under combined pesticide and temperature stress, and could further inform sustainable agricultural practices and pollinator conservation efforts.