Abstract: The efficacy of a neem insecticide (Neem AzalTM-T/S ) against early (1st instar) and late (3rd-4th instars) stage beet armyworm, Spodoptera exiqua (Hubner) (Lepidoptera: Noctuidae) larvae was assessed at different concentrations ( 0.5, 1, 1.5, 2, 2.5 ml L-1 ) and time of exposure in field cage and leaf dip assays using cotton plant. Overall results of both assays indicated that both level of concentration and time of exposure had significant effects on mortalities of larvae. Some treatments caused significant mortality as early as 2 days after exposure in the field cage study. However, none of the concentrations in leaf dip assay led to mortality earlier than 6 days after exposure. Neem over 1 ml L-1 caused complete (100%) mortality of early stage larvae in both assays. Treatments reduced number of leaves fed by larvae significantly, thus causing weight loss in individuals. No larvae could develop to pupa in treatments that received the test material at concentration levels higher than 1 ml L-1. In general, effects occurred in a dose dependent manner. Based on our findings and evidence in the literature, the neem insecticide could be useful as a biorational product in management of S. exiqua in cotton agroecosystems.