Water extracts of three plant species, i.e. Azadirachta indica (Neem), Cassia fistula (Amaltas) and Calotropis procera (AK), to test their pesticidal effect, were tried separately and in mixture as growth inhibitor and pesticide in the laboratory against Plusia orichalcea, a serious defoliator of nursery plants being environmentally safe for this purpose seed of A. indica, bark of C. fistula and leaves & tender shoots of C. procera were used The reduction in larval body weight in treated larvae was 74 19% to 78.92% over control in case of C. procera and the mixture after 12 and 6 days of treatment, respectively Mean larval period was extended upto 22 days in the mixture treatment while it was 11.5 days in control However, mean pupal period was shortened to 6 days by C fistula as compared to control, which was 12.5 days. 100 percent mortality was caused by A. indica after 3 weeks. The overall maximum mortality caused by A. indica, C. fistula, C. procera, the mixture and control was 100%, 75.0%, 41.67% and 25.0% respectively. Statistically, the difference in mortality between A. indica and C. fistula: C. procera and control; among C. fistula. C. procera and the mixture was non-significant. The three plant species inhibited growth of P. orichalcea by retarding larval body weight and prolonging larval period. The mortality was heavy.