Share This An insecticide used to control pest infestations on squash and pumpkins significantly hinders the reproduction of ground-nesting bees — valuable pollinators for many food crops, a new University of Guelph study has revealed. An insecticide used to control pest infestations on squash and pumpkins significantly hinders the reproduction of ground-nesting bees — valuable pollinators for many food crops, a new University of Guelph study has revealed. This first-ever study of pesticide impacts on a ground-nesting bee in a real-world context found female hoary squash bees exposed to imidacloprid dug 85 per cent fewer nests, collected less pollen from crop flowers and produced 89 per cent fewer offspring than unexposed bees.