Comparative studies on insect species of cowpea (Vigna unguiculata) (L) walp in two agro-ecological zones during the early cropping season, in Delta State, Southern Nigeria

Abstract

The study took place during the early planting season of 2005, in Asaba and Abraka, both in Delta State, Southern Nigeria. Asaba occupies the drier northern part of the state while Abraka, in the south, experiences a more humid weather. Insect species that decimate cowpea (Vigna unguiculata (L.) Walp in both locations, about 135 kilometres apart were identified and compared. The results showed that the occurrence and distribution of insect species followed different trends. Asaba recorded 10 insect orders, 34 families and 50 species, compared to Abraka with 8 orders, 25 families and 37 species in the same season. The dominant species in both locations were coleoptera. Asaba recorded slightly more coleoptera, heteroptera, diptera, hymenoptera and lepidoptera than Abraka. Conversely, there were slightly more orthoptera than Asaba. Ootheca mutabilis Sahl, Aphis craccivora Koch, Megalurothrips sjostedti Tryb, Maruca vitrata Fab, and coreid bugs such as Cravigralla tomentosicollis Stal, Anoplocnemis curvipes Fab, C. shadabi Doll, Aspavia armigara Fab, Nezara virudula L, Mirperus jaculus Thnb were the commonest major insect pests on cowpea at Asaba and Abraka. More insect species occurred at Asaba than Abraka in the early season.