Psara bipunctalisF. (Lepidoptera. Pyralidae) has been identified as a serious defoliating insect pest ofAmaranthus cruentusin the southern part of Nigeria. A brief life cycle study carried out at ambient temperature of 28 C showed four different larval instars with pre‐pupal and pupal stages all lasting between 21 and 22 days. Three concentrations of primiphos‐methyl were evaluated for the control ofP. bipunctalisin the field. Pirimiphos‐methyl at 0.57 kg/ha a.i. gave the optimal control of this defoliator.