AbstractMotivationImports of pesticides, especially herbicides, almost tripled in value across West Africa between 2005 and 2015. This remarkable increase has been driven by falling prices of generic pesticides, rising costs of farm labour for weeding, rising demand for farm produce, and the recent invasion of an exotic pest from the Americas, the fall armyworm (Spodoptera frugiperda).Despite rapid growth in pesticide markets, policy enforcement has not kept pace. As a result, fraudulent pesticides—often underdosed—now account for roughly one‐third of pesticides sold in the region. Fraud on this scale compromises agricultural growth, human health and environmental safety.PurposeThis article aims to assess the consequences of rapidly growing pesticide markets for farmers, traders and policy‐makers.Approach and methodsSeven national studies of pesticide markets and policy implementation—in Côte d’Ivoire, Gambia, Ghana, Guinea, Mali, Nigeria and Senegal—provide empirical evidence for this article. Following reviews of existing documents and statistics, each study involved structured interviews with regulators, policy‐makers, traders and farmers. Multiple feedback sessions with key regional stakeholder groups vetted core findings.FindingsThe investigations reveal rapid changes in the structure and performance of pesticide supply chains, including a major proliferation of generic brands and unlicensed traders, high levels of fraud, and wide variability in pesticide quality. In response, four broad regulatory models are emerging across Africa: (1) purely national testing, registration and monitoring; (2) harmonized regional protocols for testing, with national registration and monitoring; (3) regional testing and registration with national monitoring; and (4) regional testing, registration and monitoring. Purely national models are most common, but they prove costly for Africa’s many small countries.In all models, weaknesses in post‐registration monitoring and enforcement mean that risks to human health and the environment go largely unmonitored.Policy implicationsThe findings suggest several practical avenues for improving agricultural input quality and environmental safety. In the short term, stakeholder coalitions of responsible traders, farmer groups and regulators can campaign for authentic products, researchers need to step up environmental monitoring of pesticide use and impacts, and pest control specialists appear poised to continue encouraging integrated pest management to economize on use of chemicals. In the medium term, moves to regional harmonization and co‐operation reduce opportunities for smuggling and enable regional pooling of scarce technical personnel, while policy‐makers seek feasible ways of expanding resources for registration and monitoring systems commensurate with the rapid increases in pesticide use.In political economy terms, current pest invasions open a window of opportunity potentially enabling necessary structural reform of pesticide policies and regulatory systems.