Stage-specific insecticidal characteristics of a nucleopolyhedrovirus isolate from Chrysodeixis chalcites enhanced by optical brighteners

Background Chrysodeixis chalcites is a major noctuid pest of banana crops in the Canary Islands. The stage-specific susceptibility of this pest to C. chalcites single nucleopolyhedrovirus (ChchSNPV-TF1) was determined, as well as the effect of selected optical brighteners as enhancers of primary infection. Results Susceptibility to ChchSNPV-TF1 occlusion bodies (OBs) decreased as larval stage increased; second instars (L-2) were 10 000-fold more susceptible than sixth instars (L-6). Virus speed of kill was 42 h faster in L-2 than in L-6. OB production increased in late instars; L-6 larvae produced 23-fold more OBs than L-4. Addition of 10 mg mL(-1) Tinopal enhanced OB pathogenicity by 4.43- to 397-fold depending on instar, whereas 10 mu L mL(-1) Leucophor resulted in potentiation of OB pathogenicity from 1.46- to 143-fold. Mean time to death decreased by 14 to 26 h when larvae consumed OBs in mixtures with 10 mg mL(-1) Tinopal, or 10 mu L mL(-1) Leucophor, although in these treatments OB yields were reduced by up to 8.5-fold (Tinopal) or up to 3.8-fold (Leucophor). Conclusion These results have clear applications for the use of ChchSNPV-TF1 as a biological insecticide in control programs against C. chalcites in the Canary Islands. (c) 2013 Society of Chemical Industry