A novel Helicoverpa armigera Nucleopolyhedrovirus (HearNPV-IR18 isolate) formulation on hemocyte cultures of cotton bollworm (Helicoverpa armigera Hübner)

Abstract

The Helicoverpa armigera nucleopolyhedrovirus (HearNPV) is the active ingrediant biopesticide used to manage larvae. However, the effectiveness of HearNPV is limited by ultraviolet (UV) radiation. This study was conducted to develop a new formulation of HearNPV that is more tolerant to UV without compromising its efficiency. A microencapsulated formulation of HearNPV was increase its resistance to UV. For this, the virus was produced using cell lines established from H. armigera hemocytes in two media (Grace’s and EX-CELL 420). The microencapsulated formulation consisted of two different formulas. Formula A included cotton seed kernel extract, boric acid, glycerol, egg white, Bran, and sugar and Formula B included sodium alginate, gelatin, molasses and starch. The results showed that the microencapsulated formulation B exhibited higher photostability with an efficacy (84. 7 ± 4 %) and an original activity remaining (OAR) of 91.31 ± 2. 9 % after 72 h of exposure to UV by 385 nm. The average percentage of OAR in control HearNPV and formulation A was 10. 22 ± 1. 8 % and 45. 33 ± 3. 6 % respectively, after 72 h of UV exposure, with no significant statistical differences between control and formulation A. The evaluated microencapsulation mixture B had good potential to protect HearNPVs microparticles against UV inactivation. Furthermore, in EX-CELL 420 medium, virulence of the HearNPV close to that of OBs grow in the insect, with a LC50 of 6.58 × 105 OBs/mL. Therefore, the current study aimed to establish a novel and more stable pathogenic formulation in order to manage the cotton bollworm in the field.