Abstract: Plumbagin, a 1, 4-Naphthalenedione isolated from the Plumbago indica, exhibited growth regulating activity in the larvae of Pericallai ricini. The fourth instar and fifth instar larvae were topically treated with 10, 20, 25, 35, 50, 75 and 100 mg mL-1 concentrations of Plumbagin, in solvent acetone. Interference in moulting process, ecdysial failure and blockage of adult emergence were the important morphogenetic abnormalities observed which resulted in the formation of larval-pupal intermediates, abnormal pupae and deformed non-viable adults. Results suggest that Plumbagin shows an effective insect growth regulating activity and exhibits great promise in suppressing the population of P. ricini.