author(s)
R Channakeshava and VT Sannaveerappanavar

abstract
The influence of five host plants viz., fieldbean, pigeonpea, chickpea, tomato and cotton on the activity of the nuclear polyhedrosis virus against the American bollworm, Helicoverpa armigera (Hbn.) and the effect of host plant surface on the activity of HearNPV were studied. Median lethal time (LT₅₀) and Median lethal concentration (LC₅₀) in third instar larvae of H. armigera indicated that cotton and tomato plants had higher adverse effect on the virulence of the virus resulting in lower larval mortality followed by chickpea, pigeonpea and fieldbean. The yield of polyhedral occlusion bodies (POB’s) per larva was highest from the larvae that fed on field bean foliage and was least from the larvae that fed on cotton. The LT₅₀ values increased as the duration of contact between the HearNPV and the leaf surface increased irrespective of host plants and doses of the virus.