Insecticide selectivity and behavioral response of the earwig Doru luteipes M.R. Campos, M.C. Picanço, J.C. Martins, A.C. Tomaz, R.N.C. Guedes * Departamento de Entomologia, Universidade Federal de Viçosa, Viçosa, MG 36570-000, Brazil article info Article history: Received 30 April 2011 Received in revised form 20 August 2011 Accepted 22 August 2011 Keywords: Biocontrol agent Fall armyworm Insecticide toxicity Non-target impact Insecticide side-effects Predator abstract Insecticide lethal and sub-lethal effects on non-target species are a focus in pest management programs. However, such studies are usually centered in relatively few groups of natural enemies of insect pests. Earwigs, although insect pest predators of key importance in Neotropical maize fields, have received very little attention. The earwig Doru luteipes (Sccuder) (Dermaptera: Forficulidae) is one of the main pred- ators of the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae). Both species were subjected to toxicity and selectivity studies with the insecticides chlorantraniliprole, chlorfenapyr, chlorpyrifos, l-cyhalothrin, deltamethrin, etofenprox, methomyl and spinosad. The behavioral locomo- tory response of D. luteipes to these compounds was also assessed. Concentration-response bioassays indicated very low potency of chlorantraniliprole (>550,000 less toxic), followed by spinosad (>3,500 less toxic) and etofenprox (>1,100 less toxic) as compared to chlorpyrifos, the most toxic insecticide studied against this earwig species. These same three compounds exhibited the highest selectivity when comparing the earwig with its prey, the fall armyworm. Time-response bioassays using the insecticide label rates recommended against the fall armyworm confirmed the high selectivity of chlorantraniliprole and etofenprox, in addition to deltamethrin and methomyl. Again chlorpyrifos exhibited the lowest levels of selectivity. Exposure of the earwig to insecticide-treated surfaces indicated that spinosad reduced the locomotory activity of the adults probably increasing their insecticide exposure, while they avoided chlorfenapyr-, etofenprox-, and chlorpyrifos-treated surfaces. Chlorantraniliprole and etofenprox seem the most promising compounds for use against S. frugiperda whilst preserving populations of D. luteipes. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Insecticide selectivity for natural enemies is widely recognized as a key component of insect pest management, in addition to exhibiting potential consequences to arthropod pest resurgence (Ripper et al., 1951; Metcalf, 1980; Croft, 1990; Hardin et al., 1995). The assessment of pesticide side-effects on natural enemies, although historically relying heavily on acute lethal effects, has been expanding to encompass the growing concern about population-level and sub-lethal effects of these compounds (Haynes, 1988; Stark and Banks, 2003; Desneux et al., 2007; Guedes et al., 2009). Efforts have remained restricted to few groups of natural enemies, namely parasitic wasps, ladybugs, lacewings, and predatory bugs and mites (Haynes, 1988; Stark and Banks, 2003; Desneux et al., 2007). Earwigs for instance have received little attention, despite of their importance as natural enemies of some major insect pest species (e.g., Cruz et al., 1995; Fenoglio and Trumper, 2007). Most earwigs are generalist predators and, as such, are usually regarded as important natural control agents of agricultural insect pests (Buschman et al., 1977; Strandberg, 1981; Godfrey et al., 1989; Kharboutli and Mack, 1991). The earwig Doru luteipes (Sccuder) (Dermaptera: Forficulidae) is recognized as a key mortality factor of the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae), the main pest of maize and other crops in Neotropical America (Reis et al., 1988; Valicente and Barreto, 1999; Cruz, 2007; Sueldo et al., 2010). This earwig species has also been recom- mended by the Maize and Sorghum Agricultural Research Center of the Brazilian Agricultural Research Corporation (EMBRAPA Milho e Sorgo, Sete Lagoas, MG, Brazil) for augmentative releases for the biological control of S. frugiperda in Brazil (Cruz, 2007). Despite the reported importance of D. luteipes as biocontrol agent of S. frugiperda and the intensive insecticide use against this pest species (Andrews,1988; Adamczyk et al.,1999; Michereff-Filho et al., 2002; Badji et al., 2004; Cook et al., 2004), little is known about the effect of insecticides on this predator. D. luteipes has been subjected only to broad-spectrum insecticide impact assessments where side-effects to this predator were reported (Robertson, 1991; Sauphanor et al., 1993; Michereff-Filho et al., 2002; Badji et al., * Corresponding author. Tel.: þ55 31 3899 4008; fax: þ55 31 3899 4012. E-mail addresses: guedes@ufv.br, rncguedes@gmail.com (R.N.C. Guedes). Contents lists available at SciVerse ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro 0261-2194/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2011.08.013 Crop Protection 30 (2011) 1535e1540