Processing of cassava roots into flour or starch results in different waste products, which include a yellowish liquid referred to in Brazil as manipueira. This wastewater contains large quantities of cyanide formed from the hydrolysis of cyanogenic glycosides, which acts as natural plant defence. Studies conducted in Brazil over the past 30 years have looked into the possible applications of cassava wastewater in agricultural processes such as pest management. A number of studies have demonstrated its potential as a pesticide against nematodes, fungi and arthropods. Therefore, this byproduct of cassava production holds potential as a natural pesticide. Here we describe the cyanogenic glycosides of cassava and the factors that affect their content and cyanogenic potential in the plant and the chemical composition of cassava wastewater; we also review what is known about the effects of this effluent as a pesticide against arthropods and pathogens. Challenges for broader use and new avenues for further research on this topic are also proposed.