Synergistic effect of entomopathogenic fungus Fusarium oxysporum extract in combination with temephos against three major mosquito vectors

Abstract

Mosquito control using chemical insecticides is facing a major challenge due to development of insecticide resistance. Improving the efficiency of existing insecticides using synergistic secondary metabolites of biological origin is increasingly being researched. Herein, we evaluated the toxicity of Fusarium oxysporum extract alone and in binary combinations with temephos, on larvae and pupae of Anopheles stephensi, Aedes aegypti and Culex quinquefaciatus. F. oxysporum extract was characterized using TLC, FT-IR and GC-MS. After 24 h of exposure, the binary combination of temephos + F. oxysporum extract (1:1 ratio) was highly toxic to larvae of An. stephensi (LC₅₀: 35.927 μg/ml), Ae. aegypti (LC₅₀: 20.763 μg/ml) and Cx. quinquefasciatus, (LC₅₀: 51.199 μg/ml). For pupae LC₅₀ values were 38.668, 26.394, and 72.086 μg/ml, respectively. Histology studies of mosquitoes exposed to F. oxysporum extract showed vacuolation in epithelium, as well as in adipose, and muscle tissues of larval midgut. Overall, our results show that the synergistic combination of temephos and F. oxysporum extract is highly effective to control mosquito young instars.

Keywords:

• Fusarium oxysporum
• temephos
• Zika virus
• FT-IR
• GC-MS
• histopathology

Acknowledgements

The authors are grateful to Periyar University for providing financial support under University Research Fellowship Scheme (Ref No. PU/AD3/URF/16169/2016). We also thank the Institute of Vector Control and Zoonoses (IVCZ) Hosur for supplying eggs as well as the Vellore Institute of Technology (VIT) for FT-IR and GC-MS analysis.