Abstract:
Maize (Zea mays) is an important staple food crop for a sizeable proportion of the teaming human population in sub-Sahara Africa. The availability of maize is often hindered by infestation of insect pests which constitutes a major setback in its production and storage. This study sought to determine the influence of intrinsic factors of maize such as heavy metals, antinutrients, varietal differences in the physical and morphology of the maize grain on the development of the maize weevil, Sitophilus zeamais. Fifteen elite maize varieties, (BR 9943 DMR SR, IWD C2 STN F2, TZEY POP DT STRC4, SUWAN 1 – SR, SAMMAZ – 26, SAMMAZ 39F, SAMMAZ – 35, SAMMAZ – 16, TZL COMP4 DTC4, TZL COMP3 C2DT, SAMMAZ 29, SAMMAZ – 15F, PVA 8 SYN, PVA 2 SYN and TZEE W POP STR DT C5) obtained from the seed unit, International Institute for Tropical Agriculture (IITA), Ibadan, Oyo state, Nigeria were used for this investigation. Results obtained indicated oviposition as a major index of resistance (r = 0.99) in a no-choice test. Based on Dobie’s formula, the variety TZL COMP4 DTC4 was resistant to S. zeamais in F1 generation and likewise TZEE W POP STR DT C5 and SAMMAZ 29 were resistant to S. zeamais with zero adult emergences in F2 and F3 generations. These two varieties had zero susceptibility indices in F2 and F3 generations but with moderately resistance susceptibility indices of 3.70 and 0.80 in F1 generation respectively. The most susceptible variety to Sitophilus zeamais was PVA 8 SYN having the highest F3 progeny of 43.00%. In all the generations, PVA 8 SYN susceptibility indices ranged from 9.00 - 15.55. These observations were further corroborated by PCA and the significant parameters specified was subjected to cluster analysis, categorizing the fifteen varieties into three clusters namely not susceptible (SAMMAZ – 26, SAMMAZ 29, TZL COMP3 C2DT, SAMMAZ – 35, TZL COMP4 DTC4 and BR 9943 DMR SR), moderately susceptible (IWD CZ STN F2, TZEE W POP STR DT C5, TZEY POP DT STRC4, SAMMAZ –
16 and PVA 8 SYN) and highly susceptible varieties (SUWAN 1 – SR, SAMMAZ – 15F, SAMMAZ 39F and PVA 2 SYN). There was no significant difference (p > 0.05) in maize length and tannin content of all the varieties, but there was significant difference (p<0.05) in other parameters examined. The highly resistant group could be incorporated into farming system for Integrated Pest Management of the maize weevil infestation of stored grains
