Enhancement in Activity of Homologous and Heterologous Viruses Against the Gypsy Moth (Lepidoptera: Lymantriidae) by an Optical Brightener

Addition of a selected stilbene optical brightener (Phorwite AR) to the gypsy moth cytoplasmic polyhedrosis virus reduced the LC50 from 1.21 × 105 polyhedral inclusion bodies (PIB) per ml to 1.40 × 102 PIE per ml in gypsy moth, Lymantria dispar (L.), larvae. The brightener also reduced the LT50 for this virus from 13.2d to 8.4 d (1 × 106 PIB per ml). Whereas the gypsy moth is not susceptible to such viruses as the Autographa nuclear polyhedrosis virus and the Amsacta entomopoxvirus, addition of Phorwite AR to suspensions of these viruses resulted in susceptibility.