Development and Evaluation of Microencapsulated Formulations for Enhanced Stability and Efficacy of Helicoverpa armigera Nucleopolyhedrovirus (HaNPV)

Abstract

Helicoverpa armigera nucleopolyhedrovirus (HaNPV) is a species-specific baculovirus used as a biological control agent against Helicoverpa armigera. This study developed and evaluated microencapsulated HaNPV formulations using three biodegradable polymer systems: gelatin-carboxymethyl cellulose (gelatin-CMC), starch, and sodium alginate-chitosan. The formulations were prepared using polymer-based encapsulation procedures and assessed under laboratory conditions for ultraviolet-C (UV-C) protection, polyhedral occlusion body (POB) retention, larvicidal activity, and lethal-time parameters. UV-C exposure was evaluated at 10, 20, and 30 min, while larval mortality was recorded at 24 h intervals for seven days. After 10, 20, and 30 min of UV-C exposure, gelatin-CMC retained 75.0%, 50.0%, and 25.0% of POBs, respectively. The corresponding values were 40.0%, 20.0%, and 0% for starch; 70.0%, 40.0%, and 20.0% for sodium alginate-chitosan (5 mL); and 62.5%, 46.9%, and 31.3% for sodium alginate-chitosan (10 mL). Larval mortality increased progressively with exposure time. The sodium alginate-chitosan (5 mL) formulation produced 88.5% observed mortality and 87.18% corrected mortality at 168 h. The sodium alginate-chitosan (10 mL) formulation showed the shortest LT₅₀ (83.6 h) and LT₉₀ (183.6 h), followed by the 5 mL formulation. These findings indicate formulation-dependent performance: gelatin-CMC provided the greatest POB retention during UV-C exposure, whereas sodium alginate-chitosan formulations produced faster and greater larvicidal activity. Microencapsulation therefore improved the laboratory stability and biological performance of HaNPV under the tested conditions.