Effects of Neem (Azadirachta indica A. Juss) Products on Aphis craccivora and its Predator Harmonia axyridis on Cowpea

Aims: To assess the effectiveness of two neem formulations in the control of cowpea aphid, Aphis craccivora and how these affect its predator Harmonia axyridis.
Study Design: The experiment was conducted in a Randomized Complete Block Design in which cowpea was planted on raised beds.
Place and Duration of Study: The experiment was conducted on an experimental farm of the Department of Theoretical and Applied Biology, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana during the minor rainy season of 2009.
Methodology: Two neem-based products were prepared from dried neem seeds: aqueous neem kernel extract (ANKE) and neem kernel powder (NKP). A standard chemical insecticide, lambda cyahalothrin was used as a reference insecticide and a control. There were four treatments and four replications. The neem formulations and chemical insecticide were sprayed onto cowpea plants to control A. craccivora. Data were collected on numbers of A. craccivora, H. axyridis and number of damaged leaves as well as the yield of cowpea.
Results: Significantly more A. craccivora were collected on the control plots than on the treated plots (P= 0.020). The numbers of A. craccivora on ANKE and NKP-treated plots did not differ significantly (P=0.320). Harmonia axyridis numbers on the various treatments did not differ significantly (P=0.301). Significantly more leaves were damaged on the control plots than the treated plots (P=0.012) but damaged leaves on the 2 neem-treated plots did not differ significantly.
Conclusion: The two neem products were effective in reducing the population of A. craccivora. Thus application of neem products can be used as an alternative to chemical insecticide to control A. craccivora.