Resistance to Phosphine In Rice Weevil <i>Sitophilus oryzae</i> (L.) from South India

Abstract

Rice weevil Sitophilus oryzae (L.) is one of most serious insect pests of stored grains. Management of this is thus vital and fumigation with phosphine gas is the most common method. However, overreliance on this has resulted in the development of heritable resistance in S. oryzae. The detection of frequency and distribution of phosphine resistance is crucial for the development of resistance management strategy. This study assesses the frequency, strength and distribution of phosphine resistance in S. oryzae populations from four southern states of India viz., Tamil Nadu, Kerala, Andhra Pradesh and Telangana. The bioassay results revealed that all these survived at both the discriminating concentrations of 0.04 and 0.25 mg/ l. There were no susceptible and weak resistant populations, and exhibited varied frequency of strong resistance ranging from 13.33 to 80.90%. The populations from Pudukottai (80.90%) recorded high frequency of strong resistance followed by Trichy (68.97%) and Tirunelveli (67.82%) ones; the one from Thiruvarur exhibited lowest (13.33%). The results indicated that the resistance to phosphine in S. oryzae was common and prevalence of strong resistant individuals was prevalent across the sampled regions.