Lethal and sublethal effects of imidacloprid and buprofezin on the sweetpotato whitefly parasitoid Eretmocerus mundus (Hymenoptera: Aphelinidae) Fariba Sohrabi a, * , Parviz Shishehbor a , Moosa Saber b , Mohammad Said Mosaddegh a a Department of Plant Protection, Faculty of Agriculture, Shahid Chamran University, Ahvaz, Iran b Department of Plant Protection, Faculty of Agriculture, University of Maragheh, Maragheh, Iran article info Article history: Received 11 June 2012 Received in revised form 23 November 2012 Accepted 30 November 2012 Keywords: Bemisia tabaci Demographic toxicology Eretmocerus mundus Insecticides Lethal effects abstract The parasitoid Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) is one of the key natural enemies of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Lethal and sublethal effects of imida- cloprid and buprofezin on emergence and key biological and population parameters of E. mundus exposed during different developmental stages were studied. Doseeresponse bioassays were carried out on adult wasps using a leaf dipping method. The emergence rates of adults were reduced significantly by the field-recommended concentrations of the insecticides. However, the emergence rates were not affected either by the stage of the parasitoid at the time of exposure (larval and pupal stages), and there was no interaction between treatments and time of exposure. No significant mortality of E. mundus adults was observed following buprofezin treatment. The LC 50 of imidacloprid on adults was 4.75 ppm. The results showed that the longevity and fecundity of E. mundus adults were reduced significantly by the two insecticides, though the sex ratio of E. mundus offspring was not affected. Population parameters of the parasitoid such as R 0 , r m and T were also significantly reduced by the insecticides. Our results indicated that, in addition to lethal effects, sublethal effects should also be considered when these insecticides are applied in IPM programs for this pest. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction The sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemi- ptera: Aleyrodidae), is a serious pest of cotton, legume and vege- table crops worldwide (Mound and Halsey, 1978; Byrne and Bellows, 1991). Biotype determination of Iranian populations of B. tabaci indicated that the B biotype predominates in Iran (Rajaei Shoorcheh et al., 2008). It causes damage through direct feeding, excretion of honeydew and transmission of more than 100 plant viruses (Jones, 2003). Eretmocerus mundus Mercet (Hymenoptera: Aphelinidae) is a solitary parasitoid wasp and one of the key natural enemies of B. tabaci (Urbaneja and Stansly, 2004; Urbaneja et al., 2007). Because E. mundus is not always able to maintain whitefly pop- ulations below an economically acceptable level, supplementary chemical treatments are often needed in crops (Stansly et al., 2004, 2005). Selective insecticides that are more toxic to insect pests than to natural enemies can be useful tools for integrated pest management (IPM) programs (Croft, 1990; Hopper, 2003). Knowledge about the impact of insecticides on the natural enemies of a pest species is important for the integration of bio- logical control and chemical applications. Assessment of the lethal and sublethal effects of insecticides on natural enemies is necessary to recognize the total effect of insecticide applications (Desneux et al., 2007). Sublethal effects are defined as effects on individuals that survive exposure to a pesticide (Desneux et al., 2007). Suble- thal effects may be manifested as reductions in life span, devel- opmental rates, fecundity, changes in sex ratio and/or changes in behaviour (Haynes, 1988; Croft, 1990; Salerno et al., 2002; Stark and Banks, 2003; Desneux et al., 2004a, 2004b; Bayram et al., 2010a, 2010b). Demographic toxicology has been suggested as an impor- tant tool to evaluate the total effects of toxicants (Stark and Banks, 2003). The intrinsic rate of increase (r m ) has been recommended to assess overall effects of pesticides since this statistic is based on both survivorship and fecundity parameters (Stark and Wennergren, 1995). The chloronicotinyl insecticide imidacloprid and the insect growth regulator (IGR) buprofezin are two relatively new insecticides * Corresponding author. Current address: Department of Plant Breeding, Faculty of Agriculture, Persian Gulf University, Bushehr, Iran. Tel.: þ98 9173708661; fax: þ98 7713531534. E-mail address: fsohrabi1361@yahoo.com (F. Sohrabi). Contents lists available at SciVerse ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro 0261-2194/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cropro.2012.11.024 Crop Protection 45 (2013) 98e103