Optical brighteners as ultraviolet protectants and as enhancers in pathogenicity of Spodoptera litura (Fabricius) (Lep., Noctuidae) nucleopolyhedrovirus

Seven optical brighteners were tested using diet disc bioassays in the labo ratory to determine their effects on the protection and activity of Spodopt era litura (Fabricius) (Lep.. Noctuidae) nucleopolyhedrovirus (S/MNPV) agai nst 4th instar S. litura larvae. All brighteners tested Were found to be ef fective UV protectants and five brighteners (Blankophor BBH, Blankophor RKH , Blankophor P167, Blankophor HRS and Tinopal LPW) enhanced viral activity by 5.53-11.08 times. Viral activity was increased with the concentration of brighteners. The time required for the virus to kill larvae was reduced by 24-27% at 1% concentration of brighteners. Some infectivity of the virus w as round in the older larvae, which were resistant to S/MNPV, by adding the brighteners. On the basis of data obtained in the present study we discuss the synergistic action of optical brighteners with S/MNPV.