Effect of Grain Characteristics of Four Local Rice (Oryza sativa L)Cultivars on Development of the Rice Weevil (Sitophilus oryzae L.) [Coleoptera: Curculionidae] in South western Nigeria
ADU, B.W., OGEDENGBE, A.B., ADEYEMI, I.A, AND ADEDIRE, C.O.
Department of Biology, Federal University of Technology, Akure
Nig. J. Entomol. 33: 47 – 55 (2017)
ABSTRACT: The effects of grain characteristics of four local rice cultivars namely, Erin-Ijesha rice, lgbirno rice, Gboko rice, and Ogbese rice, on development ofthe rice weevil (Sitophilus oryzaei) was studied under ambient laboratory conditions at 30±2°C and 75 ±5 % relative humidity at Akure, Nigeria. Complete randomized experimental design was used with four replications per treatment. Proximate and mineral composition of the grains were determined using the Official Methods of the Association of Analytical Chemists and Atomic Absorption Spectrophotometer, respectively. Oviposition and adult emergence of rice weevil (Sitophilus oryzaes in relation to grain characteristics, mineral profile, and proximate composition of four rice cultivars (lgbimo rice, Ogbese rice, Erin-Ijesha and Gboko) were investigated. Highest number of eggs (69.25±0.85) laid by S oryzae was found in Erin-Ijesha rice which showed that the weevil preferred Erin-Ijesha rice to other cultivars. Highest number of adults (38.0±0.67) also emerged from Erin-ljesha rice cultivar. There was a positive significant difference (P<0.05) between the Erin-Ijesha rice and three other cultivars of rice. The lowest number of eggs (57.75 ±0.95) and the least percentage of adult emergence (28.5±0.48) laid by S oryzae was found on the Ogbese rice. The number of eggs laid and the numbers of adult emergence were correlated with other parameters. There was a strong positive correlation between eggs laid and copper (r = 0.653, P <0.05) and Cd (r = O.688P< 0.055). Also, there was a strong positive correlation between percentage of adult emergence and crude protein (r = 0.608), crude fat (r = 0.676), P (r= 0.755) Pb (r= 0.787) and Cd (r = 0.905). Erin-Ijesha rice cultivar was the most susceptible to Soryzae infestation due to high percentage of essential nutrient and mineral content, while Ogbese lice ranked least preferred rice cultivar for oviposition and development. The study has shown that grain characteristics and composition playa major role in the susceptibility of rice grains to infestation by S orvzae.
Keywords: Sitophilus orvzae, Rice cultivars, Adult Emergence, Morphological characteristics, Nutrient content.