Enhancement in Activity of Homologous and Heterologous Baculoviruses Infectious to Fall Armyworm (Lepidoptera: Noctuidae) by Selected Optical Brighteners

The nuclear polyhedrosis virus (NPV) from Spodoptera frugiperda (J. E. Smith) (SfMNPV) was the most active virus tested against fall armyworm, larvae (LC₅₀ = 8.1 PIB per mm²). No LC ₅₀s could be obtained for the alfalfa looper, Autographa californica (Speyer), NPV (AcMNPV), the celery looper, Anagrapha falcifera (Kirby), NPV (AfMNPV), the wax moth, Galleria mellonella (L.), NPV (GmMNPV), or the bollworm, Helicoverpa armigera (Hübner), NPV (HaMNPV). The addition of an optical brightener, Tinopal LPW® (1%), (Sigma Co., St. Louis, MO) significantly enhanced the activities of all NPVs. The most activie NPV/Tinopal LPW combination was SfMNPV, followed by AcMNPVm HaMNPV, AfMNPV, and GmMNPV. In terms of speed of kill, SfMNPV was the most active virus tested. When Tinopal LPW was added, the LT₅₀ was reduced by more than 35%. The addition of Tinopal LPW to the heterologous NPVs resulted in LC₅₀ and LT₅₀ values that were comparable to SfMNPV alone. Five of eight brighteners acted as activity enhancers for SfMNPV (i.e., Blankophor BBH, Blankophor HRS, Blankophor P167, Blankophor RKH, and Tinopal LPW), whereas Blankophor BSU, Blankophor DML, and Blankophor LPG did not enhance virus activity.