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This study was aimed at determining the effects of genotype differences on egg laying, larval, pupal
development and adult emergence of the cowpea seed bruchid, Callosobruchus maculatus (F.). Five cowpea
genotypes (SAMPEA 6, SAMPEA 7, SAMPEA 9, SAMPEA 10 and SAMPEA 11) developed by the Institute
for Agricultural Research (IAR) in Samaru, Zaria, Nigeria were used. Oviposition, larval development and
pupal development bioassays were carried out under ambient laboratory conditions by sampling 20 seeds at the
7th, 14th and 19th day after infestation (DAI) respectively. The number of eggs, larvae and pupae in sampled
seeds were counted and recorded. Adult emergence bioassay was done by counting daily the number of emerged
adults until 35 DAI when adult emergence stopped. Results from the study showed that the highest mean
number of eggs (41.3), larvae (28.3), and pupae (25.7) per 20 seeds at 7DAI, 14 DAI and 19 DAI respectively
occurred in SAMPEA 6. Also, more adults (80.6) were observed to have emerged from SAMPEA 6 than from
any other genotype. With respect to all bioassays in this study, SAMPEA 6 was significantly different (P<0.05)
from all other genotypes. On the other hand, SAMPEA 10 had the least mean number of eggs (14.0) and
larvae(8.0) per 20 seeds at 7DAI and 14DAI respectively and was significantly different (P<0.05) from the other
genotypes. However, at 19DAI, SAMPEA 9 was observed to have the lowest mean number of pupae (4.7) per
20 seeds and was significantly different (P<0.05) from the other genotypes. There was no significant difference
(P>0.05) in the number of adults that emerged from SAMPEA 7, SAMPEA 9, SAMPEA 10 and SAMPEA 11 at
P = 0.05.
Keywords: Cowpea genotypes, SAMPEA, Callosobruchus maculatus, oviposition and development.