Protection of grains against infestation and damage by diverse storage insect pests is an age long practice, as it ensures availability of agricultural produce and guarantees food security. This study assessed the protective bioactivity of moringa (Moringa oleifera Lam.) seed oil (MSO) against infestation by Callosobruchus maculatus (F.) in stored cowpea (Vigna unguiculata L. Walp.). Ten gram grains of three cowpea varieties (Borno brown, Gwalam and Banjara) were treated with four doses (0.1, 0.2, 0.4 and 0.6 ml) of MSO in three replicates, along with un-treated check. Data obtained on the number of eggs laid, adults emerged (F1) and severity of damage were subjected to the analysis of variance (ANOVA). Mean separation at 5% probability level was performed using the Least Significant Difference (LSD). Results indicated statistical significance (P<0.05) in the mean number of eggs laid on un-treated grains compared to grains treated with higher doses from each of the varieties. Similarly, mean number of adults emerged and severity of damage from un-treated grains were statistically significant (P<0.05) relative to the treated grains with all doses of each variety. Statistical differences in the mean number of eggs laid, adult emergence and severity of damage indicated the good potential of MSO in conferring protection to stored cowpea grains. The protective effect of MSO against C. maculatus seemed to be achieved principally through oviposition suppression and reduced or complete inhibition of adult emergence, consequently reducing or eradicating infestation risk, damage and loss of cowpea grains in storage. While the use of plant essential oils against storage insect pests is being advocated, the availability, affordability and the tendency of tainting protected grains need to be considered.
This study contributes in the existing literature, as the results of the study concur with reports of several authors, where plant essential oils was effective as a protectant against the cowpea bruchid infestation; consequently reducing or eradicating the damaging effect of the beetle.
T. I. Ofuya, Biology ecology and control of insect pests of stored legumes in Nigeria In: Pests of stored cereals and pulses in Nigeria, biology ecology and control. Nigeria: Dove Collins Publications, 2001.
S. R. Singh, R. A. Luse, K. Leuschner, and D. Nangju, "Groundnut oil treatments for the control of callosobruchus maculatus (F.) during cowpea storage," Journal of Stored Product Research, vol. 14, pp. 1998-7780, 1998.
O. O. Longe, "Investigation into fumigant effect of commertially produced eucalyptus oil and eugenia aromatic dust against callosobruchus maculatus (Fabritious)," presented at the International Conference on Biology, Environment and Chemistry, 2011.
T. I. Ofuya, Beans insect and man an Inaugural lecture series 35. Nigeria: The Federal University Akure, 2003.
R. F. Ogunleye, M. O. Ogunkoya, and F. O. Abulude, "Effect of the seed oilof three botanicals, jatropa curcas (L.) helianthus annus (L.) and cocos nucifera (L.) on the maize weevil, Sitophilus zeamais (Mots.)," Plant Product Research Journal, vol. 14, pp. 14-18, 2010.
Z. Dauda, Y. T. Maina, and B. I. Richard, "Insecticidal activity of garlic (Alium sativum (L.)) oil on callosobruchus maculatus (F.) In post-harvest cowpea (Vigna unguiculata (L.) Walp.)," Journal of Biology, Agriculture and Healthcare, vol. 2, pp. 28-35, 2012a.
Y. T. Maina, Z. Dauda, and D. M. Mailafiya, "Efficacy of aging stored neem seed oil and varietal resistance for the management of C. maculatus (F.) infesting stored cowp (Vigna Unguiculata (L.) Walp," In Storage International Journal of Crop Science, vol. 4, pp. 79-83, 2012.
Z. Dauda, J. W. Wabekwa, and M. M. Degri, "Efficacy of sesame (Sesamum Indicum (L.) seed oil in the management of callosobruchus maculatus (F.) infesting stored cowpea (Vigna Unguiculata (L.) Walp," International Journal of Crop Science, vol. 4, pp. 21-26, 2012b.
C. O. Okunola and T. I. Ofuya, "Effect of some essential plant oils on insect infestation of stored maize," African Crop Science Proceedings, vol. 8, pp. 1003-1007, 2007.
Y. T. Maina, "Evaluating the efficacy of three insecticidal spice oils for the control of callosobruchus maculatus (F.) (Coleoptera: Bruchidae) in stored cowpea in Maiduguri, Nigeria," Journal of Arid Agriculture, vol. 16, pp. 43-47, 2006.
Y. T. Maina and N. E. S. Lale, "Influence of duration of storage of insecticidal plant oil after extraction and oil-treated seeds prior to infestation on the efficacy of nee (Azadirachta Indica A. Juss) seed oil in controlling callosobruchus maculatus (F.)," Infesting stored cowpeas. Nigerian Journal of Entomology, vol. 22, pp. 54-63, 2005.
N. E. S. Lale and A. Mustapha, "Potential of combining neem (Azadirachta Indica A. Juss) seed oil with varietal resistance for the management of the cowpea bruchid callosobruchus maculatus (F.)," Journal of Stored Product Research, vol. 36, pp. 215-222, 2000.
N. E. S. Lale, "An over view of the use of plant products in the management of stored product coleoptera in the tropics," Post Harvest News and Information, vol. 6, p. 69N75N, 1995.
M. Ranasinghe and C. Dharmasena, "Effect of three vegetable oils on oviposition and egg hatchability of cowpea bruchid callosobruchus maculates," Srilanka Journal of Agricultural Science, vol. 24, pp. 42-48, 1987.
I. O. Udo, "Protectant effect of plant oils against cowpea weevil (Callosobruchus Maculatus) on stored cowpea," ARPN Journal of Agricultural and Biological Science, vol. 6, pp. 58-61, 2011.
M. Ramzan, "Efficacy of edible oils agains pulse beetle, callosobruchus maculatus," Journal of Insect Science, vol. 7, pp. 37-39, 1994.