Large scale trials were undertaken in Tanzania in order to assess the effectiveness of spray applications of insecticide as protectants of maize cobs against infestation by Prostephanus truncatus (Horn) and Sitophilus oryzae (L.) and S. zeamais Motsch. In general, protection of cobs was not as effective as the protection afforded to insecticide-treated grain. However, in simulated farm stores excellent protection was obtained either by applying permethrin as a dilute dust to grain or by applying it as a spray to cobs with sheathing leaves intect. Paddy husk ash also provided good protection when applied to maize grain. The treatment of maize cobs by spraying may provide the small scale farmer with a viable and more traditionally compatible alternative to the currently recommended practice of shelling maize and treating it with a dilute insecticide dust.