Effects of Cowpea Seed Resistance and larval Competition on the Development and Survival of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae)
OFUYA, T.I. and ADEDUNTAN, S.A.
ABSTRACT: The cowpea seed beetle, Callosobruchus maculatus (F.) damages stored seeds of cowpea, Vigna unguiculata (L.) Walp., an important protein source in human diet in Sub-Saharan West Africa. A major approach to the control of beetle is use of seed
resistance. The effects of seed resistance in cowpea and larval competition on the development and survival of C. maculatus had not been .adequately elucidated. In this study; a known susceptible (Ife Brown) and three resistant varieties of cowpea (IT84S-2246-4, IT85F-2205 and IT90K-391) were subjected to three different levels of larval infestation (one,five and ten larvae per seed) at 30 ± l°e and 50 ± 10% relative humidity. A beetle colony derived from infested cowpea seeds in a local market Akure, Nigeria, was employed. Beetle development and larval survival to adult emergence in
the cowpeas, were measured. The results confirmed that IT90K-391, ITu5F-2205 and (T84S-2246-4 were less susceptible to C. maculatus than Ife Brown. It was observed that in the susceptible and resistant cowpeas, development time was not affected by level of larval infestation. Percentage adult emergence decreased significantly (P<0.05) with increase in level of larval infestation in the resistant cowpeas. The significance of
these observations is discussed.