Host Preference of Rice Weevil (Sitophilus oryzae L.) to Five Rice Cultivars From Northern Iran

Host preference of rice weevil, (Sitophilus oryzae L.), was studied on five native and commercial Iranian rice cultivars as Gerdeh, Beenam, Taarom, Neda and Fajr, at two constant temperatures of 25 and 30±1°C, 75 ± 5% RH, and absolute darkness. Adult attraction to kernels, female fecundity in a 10 day interval of reproductive period, and developmental time were compared amongcultivars and temperatures. Adult attraction to kernels was studied by exposing 50 newly emerged adults to rice seeds for one week. The data indicated that Gerdeh and Beenam were the most attractive cultivars as on the average, 12.07 and 11.72 insects from overall 50 insects/dish/day (class A) were counted on them, respectively. On the other hand, Fajr attracted only 6.56 insects/dish/day (class C). The most fecund females were reared on Gerdeh (class A), Taarom (class B), Neda (class BC), Fajr and Beenam (both class C) with an average fecundity of 18.73, 13.1, 9.9, 6.47 and 6.23 offspring/female, respectively. Both parental age and temperature influenced the numberof male offsprings significantly, while females were affected only by the former. In all cultivars the sex ratio (% females) at 25°C was higher compared with 30°C. Developmental time was significantly (α=0.01) shorter at 30°C than 25°C. It ranged from 35.53 – 40.22 days at 30° C compared with 40.39 – 43.3 days at 25°C in different cultivars. It seems that Fajr and Neda show a relative resistance to rice weevil whereas Gerdeh and Taarom are relatively susceptible cultivars. Beenam showed different effects on the pest in the two temperatures.