Variations of Flower Thrips (Megalurothrips sjostedti) and Pod Borer (Maruca vitrata) Pests and Cowpea Flower Abortion Under Caging and Deltamethrin Spray Conditions

Experiments were conducted in the field to determine the effect of caging and Deltamethrin on abortion of cowpea flower and the population of Megalurothrips sjostedti and Maruca vitrata pests. Caging and complete protection of plants with Deltamethrin contributed to a substantial reduction of adults and larvae of M. sjostedti, as well as larvae of M. vitrata in the Sudano-sahelian and the monomodal Humid-forest rainfall zones. The aborted flowers were greater in the Sudano-sahelian than the monomodal Humid-forest rainfall zone. Contrary to the expectations, flower abortion was greater in caged-Deltamethrin than uncaged-Deltamethrin and uncaged-unsprayed treated plants. The flower abortion attributed to M. sjostedti was low and estimated to 2% in the Sudano-sahelian zone in 2001, and 5% in the monomodal humid-forest rainfall zone. The caging effect was 2% in the Sudano-sahelian zone in 2001, and 17%, respectively during the first and the second seasons of 2004 in the monomodal humid-forest rainfall zone. Uncaged-Deltamethrin treated plants produced more pods per plant than caged-Deltamethrin and uncaged-unsprayed plants. This study demonstrates that the flower abortion of cowpea mostly occur naturally; it also suggests that although caging and Deltamethrin can considerably reduce M. sjostedti and M. vitrata pests in field grown cowpea, it can also contribute to increase flower abortion in caged cowpea, thus a reduction of yield in a given agroecosystem.