INFECTIVITY OF FALL ARMYWORM (LEPIDOPTERA, NOCTUIDAE) NUCLEAR POLYHEDROSIS-VIRUS ENHANCED BY A FLUORESCENT BRIGHTENER

Studies were designed to determine the effect of the optical brightener, Tinopal LPW, on the infectivity of two preparations each of two isolates of the fall armyworm, Spodoptera frugiperda (J. E. Smith), nuclear polyhedrosis virus (SfMNPV). The viral preparations were diluted in either water or 0.1% Tinopal and applied to the surface of meridic diet without formalin. Three-d-old fall armyworm larvae were held individually on the treated diet for the duration of the assay (8 d). The addition of 0.1% Tinopal to the virus in the bioassay greatly enhanced infectivity of the SfMNPV. LC50s in polyhedral inclusion bodies (PIB) per cup ranged from 185 to 4,910 when tested in water and from 0.0162 to 3.36 when tested in 0.1% Tinopal. LC90s ranged from 13,800 to 305,000 per cup for virus in water and from 25.4 to 5,720 PIB per cup for virus in 0.1% Tinopal.