Effectiveness of Plants Extracts and Mycoinsecticide on Management of Cowpea Flower Thrips Megalurothrips sjostedti (Thysanoptera: Thripidea) under Field Conditions

To promote the use of natural substances for better management of the cowpea thrips Megalurothrips sjostedti, the potential of aqueous extract of Azadirachta indica, Boswellia dalzielii and Metarhizium anisopliae, alone and their combinations in comparison with the synthetic chemical insecticide (Decis) were tested. The experiments were carried out in two cowpea varieties under field conditions within the Sudano-Sahelian agro-ecological zone of Cameroon. Trials were arranged in a completely randomized block design with nine treatments. The nine treatments consisted of a negative control, A. indica; B. dalzielii; M. anisopliae, A. indica+B. dalzielii; M. anisopliae+B. dalzielii; M. anisopliae+A. indica; M. anisopliae+A. indica+B. dalzielii and Decis. Each treatment replicated four times. Vigna unguiculata plants were sprayed from flowering stage thrice with insecticidal products at 5 day intervals. The density of adults and larvae thrips was assessed on 5 flowers per block during 5 days after the last spraying of treatments. Results showed that, there were more thrips on Bafia variety than B125 variety (p<0.0001). All the tested treatment significantly (p<0.0001) reduced the cowpea flower thrips of 30% for A. indica, B. dalzielii and A. indica+B. dalzielii, 75% for M. anisopliae and its various combinations, and of 90% for Decis. Plants extracts, mycoinsecticide and their combinations considerably reduced damage induced by thrips compared to the negative control. A. indica, B. dalzielii, M. anisopliae and their combinations showed ability as natural traitement for the management of thrips in V. unguiculata. These products do not only protect V. unguiculata crop from its major pest, but also preserve the environment from harmful effects induced by the use of synthetic commercial pesticides.