Abstract The beginning of the 21st century witnessed a vast and devastating upsurge in the incidence and spread of cassava brown streak ipomovirus disease (CBSD) in eastern countries of sub‐Saharan Africa that decimated crops and jeopardized food security in the region. The disease pandemic may have resulted from an increase in superabundant African whitefly populations, the insect vector, in the early 2000s, and the unintended dissemination of infected or highly disease‐susceptible cassava planting material during agricultural development and relief programmes. This plant pandemic report, one of a series of plant disease reports commissioned by the British Society for Plant Pathology, tells the story of CBSD, its history, its impact, the devastating storage root decay it triggers, and the efforts to understand the causal agent and mitigate its damaging effect on an important staple crop.