Field evaluation of extracts of five Nigerian spices for control of post-flowering insect pests of cowpea, Vigna unguiculata (L.) Walp

The insecticidal efficacy of aqueous extracts of five Nigerian spices (Piper guineense Schum and Thonn., Aframomum melegueta (Roscoe), Xylopia aethiopica (Dunal) A. Rich., Zingiber officinale L. and Capsicum annuum L.) was tested in a field study for the control of two important post-flowering insect pests, Maruca vitrata Fab. (Lepidoptera: Pyralidae) and Clavigralla tomentosicollis Stal. (Hemiptera: Coreidae) of cowpea. The extracts were applied at 10% (w/v) and sprayed every week for 4 weeks. P. guineense, followed by A. melegueta, significantly reduced (P < 0.01) abundance of the pests and decreased the damage to cowpea pods. Grain yields were significantly higher in plots treated with P. guineense and A. melegueta extracts compared to plots treated with other extracts. This technology is cheap, safe, environmentally friendly and easy to adopt by limited resource farmers in third world countries.