Paraquat applied as a directed inter-row spray gave economical control of weeds in cassava for a period of three months or more. Applications were made at rates of 0.2–0.4 kg/ha post-emergence in young cassava of 3 months or more with 15–20 cm of brown bark at the base of the stems; a repeat application was made after an interval of 10–14 days. Usually, one further spray was required to obtain acceptable weed control until harvesting, weed control being facilitated by the increased shade given by the developing crop canopy.