A popular insecticide used on farms across Canada has been shown to have dire effects on ground-nesting bees, according to new research from the University of Guelph. Female hoary squash bees, workhorse pollinators on pumpkin and squash farms, dug 85 percent fewer nests when exposed to crops treated with the neonicotinoid insecticide imidacloprid, the research indicates. Those bees also collected significantly less pollen and produced 89 percent fewer offspring, the study shows. “These populations just plummet,” said lead author Susan Willis Chan, a post-doctoral fellow at the school. The study, published recently in Scientific Reports, is the first of its kind to look at ground-nesting bees in a real-world setting, the researchers said. Ground-nesting bees are notoriously difficult for researchers to work with, Chan said, partially because their nests cannot simply be moved as they are underground. Chan said they captured female squash bees that had already been mated and …