Monitoring Susceptibility to Spinosad in Three Major Stored-Product Insect Species from Punjab, Pakistan
Monitoring Susceptibility to Spinosad in Three Major Stored-Product Insect Species from Punjab, Pakistan
Hafiz Azhar Ali Khan1,*, Waseem Akram2, Sumi Lee3, Shakir Manzoor1, Syed Rajab Ayub1, Khalil Ur Rehman1, Shinawar Waseem Ali1, Muhammad Bilal Chattha1 and Sumaira Maqsood1
ABSTRACT
Spinosad, a reduced risk environment friendly insecticide, is increasingly being used as a grain protectant in different countries. Geographical variation in susceptibility to spinosad in stored grain insect pests has been reported worldwide; however, there is a lack of information in Pakistan. In the present study, one laboratory reference strain and five field strains each of, Rhyzopertha dominica, Sitophilus oryzae and Tribolium castaneum, were collected from Punjab, and assessed for their susceptibility to spinosad via diet incorporation bioassays. Based on median lethal concentration (LC50) values, all the strains of S. oryzae and R. dominica were more susceptible to spinosad than T. castaneum strains. The resistance ratios (RRs) of field strains at LC50 values were in the range of 2.24 to 3.24 fold for T. castaneum, 3.33 to 9.00 fold for R. dominica, and 1.73 to 3.45 fold for S. oryzae. The results revealed a variation in susceptibility to spinosad in field strains. Very low levels of resistance to spinosad in field strains warrant designing resistance management strategy for stored insect pests. The baseline data regarding spinosad susceptibility determined here for these stored insect pests will therefore help to monitor resistance in the future.
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August 2018
Vol. 50, Iss. 4, Pages 1199-1600
