From nanoformulation to field performance: A sustainable biopolymer-based azadirachtin nanoemulsion for Aphis gossypii management.

This study developed a chitosan polymer based azadirachtin nanoemulsion (ANE) to improve the stability and insecticidal efficacy of azadirachtin against cotton aphid Aphis gossypii under laboratory and field conditions. The optimized ANE exhibited excellent physicochemical stability, with a hydrodynamic diameter of nanoemulsion droplets size of 137.6 nm and a zeta potential of + 43.1 mV, confirming the formation of a stable nanoemulsion. The TEM micrograph showed spherical to slightly oval-shaped droplets with an average size of 32.5 nm. Laboratory bioassays ANE exhibited superior insecticidal activity of 76.67% mortality at 400 ppm after 72 h, with LC50 and LC90 values of 165.57 and 898.31 ppm, respectively, and achieved 93.33% repellency at the LC50 concentration after 24 h. Enzyme activity analysis revealed increased glutathione S-transferase (GST) activity together with suppression of mixed-function oxidase (MFO), carboxylesterase (CarE), and acetylcholinesterase (AChE), suggesting disruption of detoxification and neural functions in the aphid. Molecular docking studies further supported the findings by demonstrating strong binding affinities of azadirachtin with key detoxification enzymes, particularly carboxylesterase (-14.8 kcal/mol) and acetylcholinesterase (-6.4 kcal/mol). Field evaluation confirmed the practical effectiveness of ANE, with the 30 and 25 mL/L treatments reducing aphid populations by 91.09% and 88.00%, respectively. Overall, these findings indicate that the ANE offers enhanced biological efficacy, highlighting its potential as an environmentally safer alternative to conventional insecticides for sustainable management of A. gossypii in cotton.