Optical brighteners enhance activity of a nuclear polyhedrosis virus against western spruce budworm (Lepidoptera : Tortricidae)

Nine optical brighteners were tested using diet-plug bioassays in the labor atory to determine their effects on the activity of Choristoneura fumiferan a (Clemens) multicapsid nuclear polyhedrosis virus (CfMNPV) against 4th ins tars of C. occidentalis Freeman. Five brighteners (Blankophor RKH, Tinopal LPW, Blankophor BBH, Blankophor P167, and Blankophor HRS) enhanced viral ac tivity, whereas 4 did not (Blankophor BSB, Blankophor DML, Blankophor LPG, and Blankophor BSU). The effective brighteners enhanced viral activity 1.76 -13.08 times. The optimal concentration of brightener for enhancing viral a ctivity was 1%. Adding brightener reduced the time required for the virus t o kill larvae by 30-72%. Further studies are required to determine whether active brighteners may enhance efficacy of CfMNPV against C. occidentalis i n the field.