This study investigated the insecticidal effects of ethanolic oil extract of Plumbago zeylanica against Plodia interpunctella infestation in stored maize grains. Oils from the plant were administered at 5, 10, 15, 20 and 25% concentrations to maize grains inside plastic containers. The treated samples were air-dried for 3 h. The three developmental stages of the moth (egg, larval and adult) were separately introduced into the treated samples, using aspirator. Mortalities were assessed at 24, 48, 72 and 9 6 h post-treatment periods as contact and as fumigant insecticides. The rates at/from 15-25% inhibited egg to hatch and adult emergence as contact and as fumigant insecticides. At 20 to 25% rates, 81 to 100% larval mortalities were achieved within 72 to 96 h post infestation periods as contact and fumigant insecticides. At 20 to 25% application rates of oil extracts as contact and fumigant, the treatments achieved 89 to 100% adult moth mortality within 72 to 96 h post infestation periods. The GC-MS analysis of the ethanolic oil extract shows that P. zeylanica has some bioactive compounds that could be co-opted into integrated management of P. interpunctella infesting stored products.
Key words: Plumbago zeylanica, Plodia interpunctella, hatchability, contact and fumigant.