Enhancement of Nucleopolyhedrovirus Activity in Helicoverpa zea (Boddie) and Pseudoplusia includens (Walker) Larvae with a Fluorescent Brightener

Abstract

The enhancement of nucleopolyhedrovirus (NPV) activity by Tinopal® LPW (Tinopal), a stilbene fluorescent brightener, was compared in Helicoverpa zea (Boddie) and Pseudoplusia includens (Walker) using an on-diet bioassay method. Enhancement of the homologous NPV of each species was compared with three heterologous NPV that have a broad host range. In H. zea, the LC50 of H. zea NPV (HzSNPV) alone was 128 occlusion bodies (OBs)/cup, and the LC50 of it and Heliothis armigera NPV (HaMNPV) did not differ significantly. The activity of both viruses improved 18.6 fold when the OB suspension contained 1.0% Tinopal. The LC50s of Autographa californica NPV (AcMNPV) and Anagrapha falcifera NPV (AfMNPV) without Tinopal in H. zea were greater than that of HzSNPV. However, the increase in activity of AcMNPV and AfMNPV at the highest concentrations of Tinopal was two to three fold greater than the increase in activity of HzSNPV. The LC50 of P. includens NPV (PiSNPV) (856 OBs/cup) alone in P. includens was similar to that of AfMNPV and AcMNPV, and much less than that of HaMNPV (19,947 OBs/cup). The addition of Tinopal to the treatment suspension of all four viruses resulted in significantly lower LC50s at all Tinopal concentrations in P. includens. The highest concentration of Tinopal (1.0%) in the OB suspension lowered the LC50 of PiSNPV by 142.7 and AfMNPV by 89.7 fold. Tinopal in the OB suspension lowered the LC50 of AcMNPV and HaMNPV, but they remained less effective than PiSNPV with Tinopal. HaMNPV at all concentrations of Tinopal was much less active in P. includens than the other viruses with or without Tinopal.