Pesticidal Activity of Plant Extracts and a Mycoinsecticide (Metarhrizium anisopliae) on Cowpea flower Thrips and Leaves Damages in the Field

The potentials of Azadirachta indica, Boswellia dalzielii aqueous extract and Metarhizium anisopliae, alone and/or in combination, as well as a reference insecticide Decis in controlling the cowpea flower thrips (Megolurothips sjostedti) were compared on two Vigna unguiculata varieties in the field. The field trials were arranged in a completely randomized block design with nine treatments, each of which was replicated four times. The nine treatments included a control, and the eight tested insecticide products. Vigna unguiculata plants were sprayed at flowering thrice with insecticide products at 5 days interval. Data assessment consisted of counting adults and thrips larvae population after three sprays, following up their dynamics, then estimating damages caused on leaves. All the tested insecticides significantly (p < 0.0001) reduced the populations and stabilized the dynamics of both adults and larvae thrips on the studied cowpea varieties. These bio-insecticides also contributed to the substantial reduction (p = 0.0002) of damages on cowpea leaves caused by thrips compared to the control treatment. The combination M. anisopliae + A. indica + B. dalzielii was the best of all treatments with nearly 90% reduction of these pests. The cowpea variety B125 was more sensitive to the pest control than the local Bafia variety. As the outcome of the study, Azadirachta indica, Boswellia dalzielii, M. anisopliae and their combinations could be considered as potential natural insecticide in the management of thrips population on V. Unguiculata in the fields. This would increase V. unguiculata yield and free environmental pollution from synthetic insecticides.