Plants Extracts and a Mycoinsecticide (<em>Metarhizium Anisopliae</em>) in Cowpea Yield Improvement in Guinean Savanah and Sahelian Savanah Agro-Ecological Zones of Cameroun

Cowpea yield improvement is done by adding agricultural inputs. The use of natural substances as pesticides is being encouraged to fight against cowpea field pests. The pesticidal potentials of aqueous extracts of Azadirachta indica and Boswellia dalzielii, Metarhizium anisopliae, alone and in combination with plant extracts, as well as the commercial insecticide Decis were tested on two Vigna unguiculata varieties in field in two agroecological zones (Guinean Savanah and Sahelian Savanah) of Cameroon. The field trials were arranged in a completely randomized block design with nine treatments including control. Each treatment was replicated four times. Vigna unguiculata plants were sprayed at flowering stage thrice with insecticidal products at 5 days interval. Data assessment consisted of counting ramifications per plant, the number of pods per block, and seed yield. All the tested insecticides significantly (p<0.0001) improved the cowpea yield in the two agro-ecological zones. The productions parameters were highly influenced by variety and agroecological zone. The extracts and their combinations were as effective as synthetic pesticide (Decis). Bafia variety recorded the highest ramification rate (37.03±1.59) when treated with the combination of M. anisopliae and A. indica in Maroua (Sahelian Savanah). The same variety also produced most important pods number (90.50±16.66) in Ngaoundere (Guinean Savanah) with the combination of A. indica and B. dalzielii. The highest seed yield (44.23±2.31) was recorded in Ngaoundere with B125 variety treated with the combination of the three treatments (A. indica, B. dalzielii, M. anisopliae). A. indica, B. dalzielii, M. anisopliae and their combinations could be considered as potential natural input in the improvement of V. Unguiculata yield. This would not only increase V. unguiculata yield but also preserves environment from the pollution due to the use of synthetic residual chemicals.