The efficacy of different aqueous dilutions of crude seed extract of Millettia ferruginea (Hochst.) Baker (1, 3, 5 and 10%) was evaluated under field conditions in terms of the level of damage and yield loss of maize caused by the maize stemborer Busseola fusca (Fuller) in Hawassa, southern Ethiopia. The insecticide lambda-cyhalothrin 5EC, applied at a rate of 16 g active ingredient/hectare, was used as the reference product. The experiment was carried out in a randomized complete block design with four replications. The maize variety A511 was planted in individual plots of 60 m2. Data on stand count, leaf infestation, bored stem and dead heart were collected weekly. Plots sprayed with the 5% concentration of Millettia showed low levels of damage (9–11% leaf infestation, 0.4% dead heart, 14–17% bored stem and < 0.2% bored ear), compared with plots sprayed with lambda-cyhalothrin. The treatments with 1 and 3% concentrations of Millettia were inferior to those with lambda-cyhalothrin and 5 and 10% concentrations of Millettia. In contrast, the treatment with the 10% concentration of Millettia led to the death of plants, thereby lowering the yield. About 80% of the total length of individual maize stalks from the untreated plots was internally tunnelled by the feeding larvae, while the internal stem tunnelling was low ( < 7%) in plants treated with Millettia at concentrations of 3, 5 and 10%. Among the treatments with Millettia, higher yields (37–48 decitonnes/hectare) were obtained from maize plots treated with 5% concentration. The use of the aqueous crude seed extract of M. ferruginea at a concentration of 5% applied two to three times is recommended for the control of B. fusca in maize.