In vivo enhancement of nucleopolyhedrovirus of oriental Armyworm, Mythimna separata using spindles from Helicoverpa armigera entomopoxvirus

When the third instar larvae of M. separata were exposed to eight varying concentrations of polyhedral occlusion bodies (POB's) of nucleopolyhedrovirus of M. separata (MsNPV) ranging from 2.6 x 10(-1) to 2.6 x 10(8) POB's/ml, the percent mortality and incubation period ranged from 16-100% and 14 to 9 days respectively. On the other hand when the same third instar larvae of M. separata were exposed to only five varying concentration of POB's of MsNPV ranging from 2.6 x 10(2) to 2.6 x 10(6), POB's/ml along with a constant dose of entomopox viral spindles from Helicoverpa armigera, the per cent mortality ranged from 63 to 100% with reduction in incubation period from 7 to 4 days respectively. The enhancement index (log10) of the virus was 2.76 or reduction of more than 500 times in LC50. The ability and the mechanism of the spindles from H. armigera entomopoxvirus to enhance the infectivity of MsNPV has been discussed.