INFLUENCE OF HOST-PLANT SURFACE ENVIRONMENT ON THE VIRULENCE OF NUCLEAR POLYHEDROSIS-VIRUS AGAINST HELICOVERPA-ARMIGERA (HBN) (LEP, NOCTUIDAE) LARVAE

The influence of 5 host plants, chickpea, pigeonpea, lablab, sunflower and cotton on the activity of the nuclear polyhedrosis virus against the American bollworm, Helicoverpa (=Heliothis) armigera (Hbn.) and the effect of different parts of cotton plants and two species of cotton on the activity of HaNPV were studied. Median leth al concentration (LC(50)) and median lethal time (LT(50)) in second instar larvae of H. armigera indicated that cotton leaf surface was the most detrimental to the virus followed by chickpea. Pigeonpea, lablab and sunflower leaves did not affect the virulence of NPV. The LT(50) values her in pigeonpea, chickpea and cotton when compared to unexposed NPV. It was the lowest on lablab followed by sunflower. Among the different plant parts of cotton, virus exposed to leaves was most affected while flowers, squares and bells did not affect the virus significantly. NPV mortality in H. armigera larvae was higher in Gossypium barbadense than in G. hirsutum. NPV+cotton seed kernel extract-based adjuvant-mix was the most effective in increasing the persistence of the virus irrespective of the varieties.