Efficacy of binary combinations of powders from selected botanicals against Callosobruchus maculatus Fabricius damage in stored cowpea seeds

The efficacy of powder mixes of two different insecticidal plants against Callosobruchus maculatus Fabricius was determined at the Entomology Research Laboratory, Department of Crop, Soil and Pest Management of the Federal University of Technology, Akure, Ondo State, Nigeria, under ambient laboratory conditions of 26 ± 4° C and 65 ± 10% RH. The powder combinations were made from Azadirachta indica leaf Thaumatococcous daniellii rhizome Eugenia aromatica dry flower buds, seeds of Piper guineense and rhizome of Zingiber officinale in a 1:1 ratio. The binary combinations were assessed at the dosages of 0.0, 0.2, 0.4, 0.6, 0.8, 1.0 and 2.0 g per 20 g of cowpea seeds in separate 250 ml plastic containers with lids, against five pairs of newly emerged C. maculatus adults. Insect mortality was recorded 24, 48 and 72 hours post treatment and the number of F1 adult emergence was recorded after up to 35 days post treatment. The combination of E. aromatica and T. daniellii, and E. aromatica and Z. officinale produced 60% and 53% mortality respectively, of adults of C. maculatus at the lowest tested dosage (0.2 g/20 g of grain), and 100% and 83% mortality respectively, at the highest tested dosage (2.0 g/20 g of grain). Oviposition and progeny production of C. maculatus were also significantly lower in treatments involving the use of these two combinations; significantly fewer seeds bore beetle eggs and adult exit holes. The combination of E. aromatica and T. daniellii, and E. aromatica and Z. officinale may be included in pest management strategies for mitigating C. maculatus damage to stored cowpea.