ENHANCEMENT OF GYPSY-MOTH (LEPIDOPTERA, LYMANTRIIDAE) BACULOVIRUS ACTIVITY BY OPTICAL BRIGHTENERS

Addition of the selected optical brighteners Leucophor BS, Leucophor BSB, Phorwite AR, Phorwite RKH, and Tinopal LPW to the gypsy moth nuclear polyhedrosis virus (NPV) reduced the LC50 from 18,000 polyhedral inclusion bodies (PIB)/ml to values between 10 (Phorwite RKH) and 44 (Leucophor BSB) PIB/ml. These brighteners also reduced the LT50 at every virus concentration tested. At the highest virus concentration (1 X 10(6) PIB/ml), LT50s were reduced from 13.9 to 7.1 d. The addition of Tinopal LPW to the virus also enhanced mortality among mature (fourth instar) larvae. The magnitude of reduction in LC50s and LT50s in gypsy moth larvae indicated that selected brighteners greatly enhanced the virulence of the gypsy moth NPV.