Abundance and Diversity of Insect Pests on Maize, Cowpea and Okra in a Comparative Experiment Testing Effects of Intercropping and Insecticide in the Cameroonian Guinean Savannah and Sudano Sahelian Agro-ecological Zones

Intercropping has been shown as a non-chemical alternative to chemical control of insect pests. Field experiments were conducted during the 2016 and 2017 cropping seasons in the Guinean Savannah (Dang-Ngaoundéré) and Sudano Sahelian agro-ecological zones (Gouna-Garoua), Cameroon. We determined the diversity of insect pests of maize, cowpea and okra and evaluated the pest control efficiency of intercropping in comparison to the application of Cypermethrin. Experimental design was a split plot arrangement in a randomized complete block with four replications. The main factor was assigned for the use of insecticide and sub plots were devoted for cropping systems.

In unsprayed plots, the cowpea crop was found to be attacked by a total of 19 different insect species. Only three of these were considered major pests at Dang (Ootheca mutabilis, Megalurothrips sjostedti, Aphis craccivora) and three more species at Gouna (Maruca vitrata, Clavigralla tomentosicolis, Anoplocnemis curvipes). For maize and okra, we recorded only two major pests (Spodoptera frugiperda, Busseola fusca and Podagrica decolorata, Bemisia tabaci, respectively). They did not differ in the two sites.

Cypermethrin significantly reduced the number of these insect pests compared to the unsprayed plots in both sites. Also, intercropping significantly reduced the major insect pests. However, in detail the results differ with the crops, with years (2016 and 2017) and between the two sites.