Studies on Spatial Distribution of Phosphine Resistance in Rice Weevil, Sitophilus Oryzae (L.) (Curculionidae: Coleoptera) Collected from Tamil Nadu Rajan T. Sonai*, Mohankumar S., Chandrasekaran S. Department of Agricultural Entomology, Tamil Nadu Agricultural University, Coimbatore, 641003, Tamil Nadu *Email: snraja_insect@yahoo.co.in
Online published on 31 August, 2017. Abstract Fumigation with phosphine gas is the most common method of stored grain insect pest control in India. However, heavy and indiscriminate use of phosphine over several years resulted in development of heritable resistance in key stored grain insect pests. No detailed information is available on the current status of phosphine resistance in Sitophilus oryzae (L.) and its spatial distributions in different geographical locations of India. Twenty two samples of S. oryzae collected from various parts of Tamil Nadu were tested through bioassay for determining the level of resistance on the basis of the response of adults to discriminating concentration of 0.04 mg L−1, for 20 h exposure. The bioassay results showed that resistance was common in all the field collected populations of S. oryzae and the level resistance ranged from 21.21 to 93.38%. Of the 22 populations tested, 54.54% showed low resistance, 22.73% were medium and 22.73% exhibited high resistance. The populations from Kumbakonam showed high level resistance (93.38%). The low level resistance was observed in Peelamedu (21.21%) population. Spatial analysis of different geographical distance and % resistance showed a negative correlation with spatial distance and level of resistance (r =-0.083 and simulated p-value = 0.8249) in S., oryzae populations collected from Tamil Nadu. Top Keywords Phosphine resistance, Sitophilus oryzae, spatial distribution, populations, level of resistance, adults, field collection, discriminating dose. Top |