Viral-enhancing activity of an optical brightener for Spodoptera littoralis (Lepidoptera: Noctuidae) nucleopolyhedrovirus

Abstract

The effect of an optical brightener on the insecticidal activity of a Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) nucleopolyhedrovirus (SpliNPV) were examined in three instars of S. littoralis. LD₅₀ values of the SpliNPV were reduced from 33 to <5, 73 to 5.7 and 342 321 to 288 412 occlusion bodies for second, third and fourth instars, respectively, by the addition of 1% Tinopal UNPA-GX. Relative potencies were >66, 12.8, and 1.2 for second-. third- and fourth-instar S. littoralis larvae, respectively. Relative mortality between the treatments with and without the brightener decreased from third- to fourth-stage larvae. In terms of speed of kill, the ST₅₀ values of the baculovirus-infected larva were reduced from 210 to 159, 213 to 147, and 207 to 165 h for second-, third- and fourth-instar larvae, respectively, by the addition of the optical brightener at biologically equivalent doses.

Keywords:

• Spodoptera littoralis
• baculovirus
• optical brightener

Partially based on a paper presented at the 38th Annual Meeting of the Society for Invertebrate Pathology and held at University of Alaska, Anchorage, Alaska, USA, on 7–11 August 2005.

Partially based on a paper presented at the 38th Annual Meeting of the Society for Invertebrate Pathology and held at University of Alaska, Anchorage, Alaska, USA, on 7–11 August 2005.

Acknowledgments

We are grateful to Emeritus Prof. Cedric Gillott (University of Saskatchewan, Canada) for the critical review and to Dr Martin Erlandson (Agriculture and Agri-Food Canada, Saskatoon Research Centre, Canada) for many helpful suggestions. We also thank Dr Huarong Li (Iowa State University, USA) for his help with the statistical analyses. This research was funded by the Biotechnology Institute of Ankara University (project no: 25) and Turkish Republic Prime Ministry State Planning Organization (project no: 004K120930-6).

Notes

Partially based on a paper presented at the 38th Annual Meeting of the Society for Invertebrate Pathology and held at University of Alaska, Anchorage, Alaska, USA, on 7–11 August 2005.