Effect of UV protectants mixed with HaNPV on POBs and larval mortality of Helicoverpa armigera Hübner

Baculovirus could be an attractive candidate for integrated pest management (IPM) because of its inherent high pathogenicity, narrow host range, and safety to vertebrates, plants and the environment. Despite these advantages, its practical application as a microbial pesticide has not been fully exploited due to rapid inactivation of the virus by sunlight (UV rays). However, additives can be used to protect the baculovirus from light degradation. The present study was carried out to test the potential of silver nanoparticles (SNPs) as UV protectants along with 1 % Tinopal® and 1 % mango leaf extract, and to develop Helicoverpa armigera Nucleopolyhedrovirus (HaNPV)-ready formulation with potential UV protectant during 2012-2013. An attempt was also made to use SNPs as an antimicrobial additive to extend the shelf life of HaNPV and to shelter the polyhedral occlusion bodies (POBs) from UV degradation after spraying in field against H. armigera Hubner on various crops. Formulated viral suspensions were exposed to UV 20 W Philips lamp (Type 5, range 285 - 320 nm) for 15 min and to sunlight at noon hours for 30 min, and 1, 1.5 and 2 hrs to determine the viability of POBs and larvicidal activity. The least reduction in POBs i.e. 5.2 %, was observed from HaNPV + 1 % Tinopal, which also recorded a 86.7 % larval mortality when exposed to UV lamp. The results was in par (p>0.05) with HaNPV alone un-irradiated. The HaNPV alone with irradiation recorded 55.1 % reduction in POBs, while HaNPV + 1 % Tinopal with exposure to sunlight protected the POBs up to 1.5 hr, with 20.5 % reduction in POBs and 83.9 % larval mortality. Exposure to for 2 hrs reduced the insecticidal activity of HaNPV even though 1 % Tinopal was used as a UV protectant. Of the additives, 1 % Tinopal was found to be effective as it protected the POBs from UV degradation and enhanced the larval mortality as compared to 1 % mango leaf extract and SNPs.