Urban landscapes may bear more responsibility for exposing bees to pesticides than previously thought.
A recent study from Purdue University, published in the academic journal Nature Communications, found honeybees gathered the vast majority of pollen from non-agriculture crops and were being exposed to both agricultural and domestic pesticides.
Entomologist Christian Krupke found pollen samples contained residues from pesticides spanning nine chemical classes, including neonicotinoids — common corn and soybean seed treatments that are toxic to bees.
The highest concentrations of pesticides in bee pollen, however, were pyrethroids, insecticides typically used to control mosquitoes and other nuisance pests. Pyrethroids are typically used where pollinators are likely to be — near homes and gardens with a diversity of flowering plants.
The study showed distinct spikes of pyrethroids in August and September, months when many homeowners spray these chemicals to knock out mosquitoes, hornets and other nuisance pests.
“Bees in our study were exposed to a far wider range of chemicals than we expected,” said Krupke. “The sheer numbers of pesticides we found in pollen samples were astonishing. Agricultural chemicals are only part of the problem. Homeowners and urban landscapes are big contributors.”
The study suggests that overall levels of pesticide exposure for honeybees in the Corn Belt could be considerably higher than previously thought, Krupke said. This is partly because research efforts and media attention have emphasized neonicotinoids’ harmful effects on pollinators and their ability to travel and persist in the environment.
Few studies, however, have examined how non-crop plants could expose bees to other classes of pesticides.