Risk assessment, cross-resistance potential, and biochemical mechanism of resistance to emamectin benzoate in a field strain of house fly(Musca domestica Linnaeus) Hafiz Azhar Ali Khan a, * , Waseem Akram b , Tiyyabah Khan a , Muhammad Saleem Haider a , Naeem Iqbal c , Muhammad Zubair b a Institute of Agricultural Sciences, University of the Punjab, Lahore, Pakistan b Department of Entomology, University of Agriculture, Faisalabad, Pakistan c Department of Plant Protection, Ghazi University, Dera Ghazi Khan, Pakistan highlights  Rapid development of resistance to emamectin was observed as a result of selection experiments.  The EB-SEL strain showed reduction in resistance to abamectin, indoxacarb and thiamethoxam.  Metabolic resistance mechanism was not responsible in developing emamectin resistance in the EB-SEL strain. article info Article history: Received 15 December 2015 Received in revised form 16 February 2016 Accepted 17 February 2016 Available online xxx Handling Editor: Jim Lazorchak Keywords: New chemicals Environmental pollution Ecotoxicology abstract Reduced sensitivity to insecticides in insect pests often results in control failures and increases in the dose and frequency of applications, ultimately polluting the environment. Reduced sensitivity to ema- mectin benzoate, a broad-spectrum agrochemical belonging to the avermectin group of pesticides, was reported in house flies (Musca domestica L.) collected from Punjab, Pakistan, in 2013. The aim of the present study was to investigate the risk for resistance development, biochemical mechanism, and cross- resistance potential to other insecticides in an emamectin benzoate selected (EB-SEL) strain of house flies. A field-collected strain showing reduced sensitivity to emamectin was re-selected in the laboratory for five consecutive generations and compared with a laboratory susceptible (Lab-Susceptible) reference strain, using bioassays. The field strain showed rapid development of resistance to emamectin (resistance ratio (RR) increased from 35.15 to 149.26-fold) as a resultof selection experiments; however, resistance declined when the selection pressure uplifted. The EB-SEL strain showed reduction in resistance to abamectin, indoxacarb, and thiamethoxam. The results of synergism experiments using piperonyl but- oxide (PBO) and S,S,S-tributylphosphorotrithioate (DEF) enzyme inhibitors and biochemical analyses revealed that the metabolic resistance mechanism was not responsible in developing emamectin resistance in the EB-SEL strain. In conclusion, the risk for the rapid development of emamectin resistance under continuous selection pressure suggests using a multifaceted integrated pest management approach for house flies. Moreover, the instable nature of emamectin resistance in the EB-SEL strain and lack of cross-resistance to other insecticides provide windows for the rotational use of insecticides with different modes of action. This will ultimately reduce emamectin selection pressure and help improving management programs for house flies without polluting the environment. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction The failure to control insect pests of economic importance in the past few decades has largely been due to over-reliance on in- secticides in Pakistan. This has resulted in the development of * Corresponding author. E-mail address: azhar_naturalist@yahoo.com (H.A.A. Khan). Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere http://dx.doi.org/10.1016/j.chemosphere.2016.02.077 0045-6535/© 2016 Elsevier Ltd. All rights reserved. Chemosphere 151 (2016) 133e137