Synergistic activity of aqueous extracts mixtures of some Nigerian plants against Maruca vitrata and Clavigralla tomentosicollis on field cowpea, Vigna unguiculata (L.) Walp

Abstract

Field experiments were conducted under rain fed conditions in two seasons to test the effectiveness of seven different plant extract mixtures for management of Maruca vitrata (Fab.) and Clavigralla tomentosicollis Stal on cowpea, Vigna unguiculata (L.) Walp. The application of 10:10% w/w of peels of Citrus sinensis + Gmelina arborea leaf extracts, fruits of Capsicum annum + Eucalyptus citriodora leaf extracts, and peels of C. sinensis + Ocimum gratissimum leaf extracts were effective in reducing the incidences of M. vitrata and C.tomentosicollis on flowers and pods of cowpea, respectively. Grain yield was subsequently increased by 3.2 – 3.5× in plots treated with these extract mixtures compared with the control check. Although, the mixtures of peels of C. sinensis + Azadirachta indica leaf, fruits of C. annum + A. indica leaf, and peels of C. sinensis + Vernonia amygdelina leaf extracts were inferior to the extracts mixtures mentioned above in effecting reasonable control of the test insect pests, they were significantly superior to the control check in the two seasons of study. The mixtures of C. sinensis + G. arborea, C. annum + E. citriodora, and C. sinensis + O. gratissimum extracts could play an important role in crop pest management for small holder farms in tropical countries and none of the extract mixtures had any phytotoxic effect on the sprayed plants.

Keywords:

• Synergism
• plant extract mixtures
• pest control
• cowpea

Acknowledgements

The author is grateful to Professors M. C. Dike and C. I. Amatobi for their invaluable suggestions during the field work which enhanced the quality of the results presented in this paper. Furthermore, my appreciation goes to Messrs Gideon Gbilin, Joyce, Innocent, Vincent, Victor and Ignatius for their technical support in data collection and to the Director, Institute for Agricultural Research, Ahmadu Bello University, Zaria for his kind permission to publish this report.