Field experiments were carried out to evaluate the yield efficacy of an insecticide Decis 2.5 EC (Deltamethrin, a pyrethroid insecticide) for the control of some insect pests of two cultivars of Bungu, Ceratotheca sesamoides Endl. in Ilorin, Kwara State. The experiment was laid out in a randomised complete block design with two treatments. Each treatment was replicated four times. Decis 2.5 EC used at the rate of 50ml/ha was sprayed at 4 weeks after planting. The damage caused by Antigastra. catalaunalis as a result of its feeding activity was cultivar dependent. The damage was significantly higher (P<0.05) on cv. ‘Pete’ than on cv. ‘Gogoro’. Insecticide treated crops of cv. ‘Pete’ had significantly (P < 0.05) better growth and yield attributes than the non treated crops. The non treated crop of cv. ‘Pete’ had a mean leaf fresh weight of 0.5 g/m2, while the treated crop had a mean leaf fresh weight of 4.85g/m2. The insecticide treatment did not have any significant effect on the yield of cv. ‘Gogoro’ as the non treated crop as well as the treated crop had a mean leaf fresh of 0.05g/m2. Insecticidal sprays should be done weekly rather than at longer intervals to prevent a complete destruction of the crops on the field.