Application of juvenile hormone analogue and optical brightener technologies to the production of Spodoptera frugiperda multiple nucleopolyhedrovirus.

Final instar larvae of Spodoptera frugiperda grew to a maximum weight of 622 ± 13 mg on diet treated with 1% piriproxyfen, a juvenile horrnone analogue (JHA). or 695 ± 17 mg on diet treated with 1% fenoxycarb, both of which were significantly greater weights than observed in larvae that developed on untreated diet (512 ± 9 mg). Virus mortality in insects inoculated with SfMNPV occlusion bodies (OBs) was approximately 50% in all treatments, reflecting the resistance of late instar S. frugiperda larvae to infection. However, JHA treatment did not result in a significant increases in the total OB yield, or OBs per mg larval weight, compared to untreated infected insects. We deterrnined whether resistance to infection could be overcome by inoculation with mixtures of OBs and optical brighteners. Potentiation of OB activity was >2500-fold in mixtures with 1% Leukophor AP or Blankophor BA, or >15-fold in mixtures with 0.1 % of either brightener, compared to SfMNPV OBs alone. We conclude that SfMNPV production was 110t increased in JHA treated larvae because the JHA did not result in a supernumerary instar in S. frugiperda. However, optical brighteners were highly effective in overcoming developmental resistance to infection in this species.