Bioefficacy of novel arginine-rich chitosan against Diamondback moth, Plutella xylostella L. (Lepidoptera: Plutellidae) infesting cauliflower

A novel arginine rich chitosan derivative (chitosan-O-arginine (CS-O-Arg)), was synthesized by O-acylation reaction of chitosan (CS) with L-arginine in the presence of catalyst sulfuric acid (H 2 SO 4 ). The physicochemical properties of CS and CS-O-Arg were standardized and characterized, to confirm the enhancement of their solubility (36.2% to 91.0%), Degree of Deacetylation (56.0% to 92.6%), Water Binding Capacity (0.64 g/g to 7.86 g/g, 12.28-fold increase) and Viscosity (0.092 Pa . s to 0.624 Pa . s) in the chitosan derivative, and the FTIR analysis indicated that acylation process has taken place in both C3-OH and C6-OH of CS. The biological activity of CS-O-Arg was evaluated against second instar larvae of Plutella xylostella by leaf dip bioassay with nine treatments, viz., 100, 300, 500, 700, 1000 ppm of CS-O-Arg, solvent alone (Glacial Acetic acid 1%), adjuvant alone (Tween 80 0.05%), standard check (Azadirachtin 1 EC @ 2 ml/lit), untreated check and replicated thrice. It was found that CS-O-Arg at 1000 ppm displayed the highest mortality (90.0%) and antifeedant activity (93.69%) after 72 h of treatment. The LC 50 and LT 50 value of CS-O-Arg was 688.64 ppm and 42.44 h, respectively. It is concluded that chitosan-O-arginine is a novel chemically synthesized eco-friendly biomolecule possessing a strong toxic and antifeedant effect against diamondback moth, P. xylostella , which can be further explored to develop as a formulation.