Abstract

                                Chitosan (Cs), a natural biodegradable polysaccharide polymer,prepared from sea waste of crustacean origin, has the potential for plantprotection application. In the present study, a novel chitosan derivative,called Chitosan-O-Arginine, synthesized from crude chitosan, wasevaluated for its chronic toxicity against second instar larvae of Plutellaxylostella by leaf dip method. The results revealed the toxic potential ofChitosan-O-Arginine, which could inflict cent per cent mortality after fourdays of continuous feeding on the 1000 ppm treated leaf, and the larvacould accomplish 0.12 mg weight (99.66% reduction) on the day beforedeath. The next lower concentration (700 ppm) resulted in the maximumlarval weight of 0.45 mg (93.71% reduction) after nine days of feeding andresulted in cent per cent mortality after the tenth day. While the untreatedlarva attained a maximum weight of 5.54 mg. All the larvae were pupatedin the next lower concentration (500 ppm) and recorded minimum pupal(1.00 mg; 80% reduction) and adult (0.73 mg; 77.45% reduction) weight,whereas the untreated pupa and adult weighed the maximum of 5.00mg and 3.20 mg. Considering the developmental period, there was nosignificant difference in the larval duration and adult life span. While therewas an extension of the pupal period by one day at 500 ppm compared tountreated larva. The larval, pupal, and adult malformations were noticedin 300 and 100 ppm concentrations. These findings suggest that chitosanwas potent in imposing chronic toxicity and growth inhibitory effect onP. xylostella larvae, and hence it can be recommended as an eco-friendlycomponent in the Integrated Pest Management module.

Key words : Plutella xylostella; Chitosan-O-Arginine; Chronic toxicity; Growth inhibition; Malformations