Yield optimization parameters for enhancing the in vivo productivity of Spilosoma obliqua nucleopolyhedrosis virus (SpobNPV) infecting jute hairy caterpillar, Spilosoma obliqua (Walker)
摘要
Studies were conducted to optimize the parameters involved in the in vivo productivity of Spilosoma obliqua nucleopolyhedrosis virus (SpobNPV) progeny viral yield necessitated for the management of jute hairy caterpillar, Spilosoma obliqua (Walker). Optimization parameters assessed for ensuring highest possible polyhedral yield comprised of effective larval instar for progressive viral infection, SpobNPV inoculum dose and post infection incubation temperature. Results revealed that third instar larvae infected with viral inoculum of 1 × 104 PIBs/ml and subjected to incubation temperature of 28°C resulted in the harvest of highest polyhedra yield viz., 1.02 × 1010 PIBs/larva in comparison to second instar larvae resulting in polyhedral yield of 9.94 × 108 PIBs/larva under similar conditions. The polyhedral yield post six days after disease progression revealed 11.88- folds increase in polyhedra harvest in third instar larvae in comparison to the second instar larvae. The estimated median lethal time (LT50) in bioassays with inoculum dose of 1 × 104 PIBs/ml decreased from 174 to 111 h in second instar larvae and from 197 –118 h in third instar larvae with increase of temperature regimes from 14 to 35 °C. Post incubation temperature studies on second and third instar larvae infected with inoculum dose 1 × 104 PIBs/ml revealed that third instar larvae resulted in the highest polyhedra yield of 9.66 × 109 PIBs/larva when subjected to incubation of 28°C on the sixth day of harvesting. Field experiments conducted at two different temperature regimes (27–29°C and 34–36°C) revealed larval reduction percentages of 68.16, 83.46 and 94.68% post 2, 4 and 7 days after spray with SpobNPV dose of 1 × 104PIBs/ml in the temperature regime of 27–29 °C.