Susceptibility level of some Nigerian hybrid and local rice varieties to Sitophilus oryzae L. (Coleoptera: Curculionidae)
Olajire A Gbaye, Olanrewaju B Ajiye
Seven rice varieties, Oryza sativa (Linnaeus), [two local Nigerian varieties namely: Igbimo and Ofada; four hybrid varieties viz: ITA 321, FARO 44, WAB 189 and WITA 4; and Aroso (Thailand imported rice)] were screened for their susceptibility to Sitophilus oryzae at ambient temperature of 28±2 °C and 70–81% relative humidity in the laboratory. Ten grammes of each rice variety were infested with eight female and four male weevils and then replicated three times with the forth uninfested replicate serving as control. The least susceptible variety with the least susceptibility index (2.2) and lowest number of adult emergence (2.00) was WAB 189 while the most susceptible with the highest susceptibility index (6.0) was Ofada. The highest adult emergence (25.33) and percentage weight loss was recorded in Igbimo while the shortest developmental period (31 days) and the longest developmental period (35 days) were observed in Ofada and ITA 321 respectively.