In this article, I examine the knowledge politics around pesticides in the United States and the role it plays in honey bee declines. Since 2006, US beekeepers have lost an average of one-third of their colonies each year. Though a number of factors influence bee health, beekeepers, researchers and policymakers cite pesticides as a primary contributor. In the US, pesticide registration is overseen by the US Environmental Protection Agency (EPA), with the required tests conducted by chemical companies applying for registration. Until 2016, the EPA only required chemical companies to measure acute toxicity for non-target species, which means that many pesticides with sublethal toxicities are not labeled bee-toxic, and farmers can apply them without penalty while bees are on their farms or orchards. In addition, California state and county regulators will typically only investigate a bee kill caused by a labeled bee-toxic pesticide, and so emergent data on non-labeled, sublethal pesticides goes uncollected. These gaps in data collection frustrate beekeepers and disincentivize them from reporting colony losses to regulatory agencies – thus reinforcing ignorance about which chemicals are toxic to bees. I term the iterative cycle of non-knowledge co-constituted by regulatory shortfalls and stakeholder regulatory disengagement an ‘ignorance loop’. I conclude with a discussion of what this dynamic can tell us about the politics of knowledge production and pesticide governance and the consequences of ‘ignorance loops’ for stakeholders and the environment.