The overall objective of this project is to characterize the indirect and interactive effects of fungicides and insecticides on native pollinator health in restored pollinator habitats. Our central hypothesis is that fungicides and insecticides impact pollinator health by altering the composition and function of critical soil and plant microbial associations that influence bee survival and behavior. These indirect influences of pollinator health can lead to ecological surprises that affect successful restoration and conservation efforts, and this project will address critical knowledge gaps about different pathways through which pesticides affect pollinators. Our project will generate a deeper understanding of the use and misuse of pesticides in pollinator conservation efforts, and discovery of the varied roles that plants, microbes and bee behavior play in pollinator health. We will test our central hypothesis, and thereby accomplish the overall objective of this proposal, by pursuing the following goals: (1) Quantify the effects of pesticide-altered soil microbiota on the health and survival of ground-nesting bees. We will accomplish this goal through a series of lab-based mesocosm experiments using live and sterilized soils derived from an ongoing field experiment that includes pesticide and fungicide addition. (2) Quantify the effects of pesticide-altered soil and plant microbiota on the health, survival, and population dynamics of "bee plant" species that are beneficial for pollinator health. We will accomplish this goal through greenhouse-based experiments using live and sterilized soils from our ongoing field experiment. (3) Determine how pesticide- and fungicide-mediated changes in soil microbiota affect foraging and nesting decisions of bees. We will accomplish this goal using lab-based behavior trials using soils inoculated with live microbes and insecticide and fungicide, and we will also document pollinator foraging behavior in the field using plants grown under controlled conditions to disentangle the relative effects of pesticides and microbe-mediated changes.