Screening of phosphine resistance in Sitophilus oryzae (L.) (rice weevil) populations in Turkey

In this study, the status and prevalence of phosphine resistance in Sitophilus oryzae (L.) (Coleoptera: Curculionidae) populations collected from Mersin and Konya Province in Turkey were investigated by conducting the discrimination concentration tests and the concentration–mortality bioassays. Discriminating concentration tests showed that 89.9 and 83.3 % populations of tested total S. oryzae populations collected from Mersin and Konya province respectively were resistance to phosphine, which reveals high prevalence of phosphine resistance in the insect sampling locations of both provinces. Moreover, discrimination low concentration (0.04 mg/l) tests indicated that 62.5 and 33.3% of total S. oryzae populations collected from Mersin and Konya province respectively had 90% or above survival rate, which showed that the frequency of high phosphine resistance in S. oryzae populations collected from Mersin province was higher than that in S. oryzae populations collected from Konya province. The concentration–mortality bioassays indicated that there were significant differences in resistance levels of S. oryzae populations collected from different provinces. Based on the resistance factors (RF) calculated by LC₅₀ values S. oryzae populations from Mersin and Konya province were 102- to 104-fold and 38- and 81-fold resistance to phosphine compared with susceptible S. oryzae population, respectively. The highest level of phosphine resistance was determined in S. oryzae populations from Mersin province, followed by those from Konya provinces, respectively. These results indicated that S. oryzae populations from Mersin province had higher phosphine resistance than those from Konya Province. In conclusion, this study showed that high levels of phosphine resistance in S. oryzae populations collected from different grain storages in Mersin and Konya province of Turkey were prevalent.