In the course of screening for novel naturally occurring insecticides from plants, the activity of a senescent (yellow) leaf extract of Melia azedarach L. (Meliaceae) was investigated. Antifeedant effects were tested on five Lepidoptera and four Coleoptera species, in laboratory choice tests. Further effects on insect feeding and survival were studied in no-choice tests with larvae and adults of Epilachna paenulata Germar (Coleoptera: Coccinellidae). In the choice tests, M. azedarach yellow leaf extract strongly deterred feeding in eight out of the nine species considered. Larvae and adults of E. paenulata which received only extract-treated food suffered higher mortality rates; larvae did not reach the pupal stage. Insects receiving extract-treated food ate less and larvae had lower body weight than their control counterparts, suggesting that the observed increase in mortality might be related to the strong antifeedant activity of the extract. The effects were significantly related to extract concentration.