Effect of two granulosis viruses on the activity of the gypsy moth (Lepidoptera: Lymantriidae) nuclear polyhedrosis virus

Two granulosis viruses (GV) were tested as enhancers for the gypsy moth nuclear polyhedrosis virus (LdMNPV). Helicoverpa armigera (Hübner) CV (HaGV) had no detrimental effect upon larval growth and development, but in combination with LdMNPV it reduced both the LC50 and the LT50 for the NPV. In addition, the combination also adversely affected the growth and development of gypsy moth larvae. The LC50 of LdMNPV was reduced by as much as 300-fold (HaGV at 10(-2) dilution) and the LT50 was reduced by as much as 18% (HaGV at 10(-2) dilution). Spodoptera frugiperda (J. E. Smith) GV reduced the LC50 of LdMNPV by as much as 13-fold but had no effect upon the LT50.