Efficacy of HearNPV formulations against Helicoverpa armigera at different sunlight exposure period

Abstract

Experiment was conducted at Department of Entomology, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola during 2011- 2013 to see the effect of natural sunlight (UV) on HearNPV formulation. Experiment was laid out in Completely Randomized Block Design replicated thrice. The aqueous and dry form of HearNPV formulations were prepared by using additives viz. Tinopal an optical brightener and silver nano particle and evaluated their capability to protect NPVs from Ultra Violet rays. HearNPV formulation were sprayed uniformly on the potted chickpea plants during noon hours. Twigs were collected at thirty minutes, One hour, One and half hours and two hours after spraying and kept in petriplates. The laboratory reared second instar larvae of H. armigera were released on each treated twig. Larval mortality was recorded at 4, 7 and 10 days after treatment. An aqueous form of HearNPV formulation, HearNPV + Silver Nano Particles @ 8 ?l /ml of HearNPV + Tinopal 1% + Sucrose 1% (T1) recorded 83.04% larval mortality at ten days after spraying which was at par with HearNPV alone unirradiated (84.21 % larval mortality) when exposed to sunlight up to one hour. Among the lyophilized form of formulations, HearNPV + Silver Nano Particles @ 8?l/ml of HearNPV + Tinopal 1% + Sucrose1% (T6) when exposed to sunlight up to one hour recorded 84.80% larval mortality at ten days after spraying which was at par with which was at par with HearNPV alone unirradiated (T12) (85.38% larval mortality) and higher than HearNPV alone irradiated. Both aqueous and lyophilized form of HearNPV showed decreasing larval mortality as compared to HearNPV alone unirradiated when exposed to sunlight up to one and half and two hours. Lyophilized HearNPV formulations recorded higher larval mortality as compared to aqueous form of HearNPV formulations at all sunlight exposure period.