Physalisperuviana shrubs were not attacked by larvae of Spodoptera littoralis. It was demonstrated that withanolide E, a steroid isolated from P.peruviana, as well as several related steroids, have insect antifeedant properties.

The effect of Margosan-0 (a commercial biochemical insecticide containing azadirachtin) on the development of larvae of Spodoptera littoralis (Boisd.) was investigated by feeding them treated cotton leaves or by topical application, followed by recording mortality until the adult stage. Seedlings of cotton were sprayed in the laboratory with varying concentrations of Margosan-0 and offered for 2 days, to larvae weighing 30-50 mg. Margosan-0 exhibited high activity down to a concentration of 2 x lo-' Yo a.i. azadirachtin in the spraying liquid.Topical application of Mar osan-0 showed that at 5 x lo-' % (0.1 pg) to 2 x lo-' % a.i. (4 yg) azadirachtin caused mortality of larvae up to pupation ranging from zero to approximately 70 YO. The ED5,, (effective dose) was 2.0 pghrva. 'Control of Spodopteru littoralis by Margosun-0 331 2.2 Bioassay Feeding of larvae on cotton leaves treated with Margosan-0Cotton plants grown in flower pots in a greenhouse at 20 "C were sprayed with an electric airless hand sprayer (Krebs 10, The0 Krebs AG, Kreuzlingen, Switzerland) with the following concentrations of Margosan-0: 0.3, 0.45, 0.60, 0.75, 0.90, 1.20 and 1.50 Yo which correspond to 1 x