A study at the University of Guelph has revealed that an insecticide used to control pest infestations on squash and pumpkins significantly hinders the reproduction of ground-nesting bees. Female hoary squash bees exposed to imidacloprid dug 85 percent fewer nests, collected less pollen from crop flowers and produced 89 percent fewer offspring.
“Because they’re not making nests and not collecting pollen, they cannot raise offspring,” said Dr. Susan Willis Chan, a Post-Doc in the School of Environmental Sciences.
Neonic imidacloprid is used by farmers to reduce the population of cucumber beetles, which are the most damaging crop pest for squash and pumpkins. The pesticide kills insects by attacking their nervous system, which can affect learning, foraging, and navigation in bees.
The study was conducted over a three-year period in which Chan and Professor Nigel Raine tested three different insecticide treatments and the long-term effects these pesticides had on bees. They found that bees exposed to anthranilic diamide sprayed onto growing plants collected significantly less pollen but had no fewer nests or offspring. They also tested neonic thiamethoxam applied as a seed treatment, which had no measurable effects. The most damaging was by far the neonic imidacloprid applied to soil.
“Farmers need to protect their crops from pests, but they also absolutely need to protect pollinators from the unintended effects of pesticides,” said Chan. “The data on this particular product are so clear that there’s really no question about what has to happen. We have to find something else.”