Non-target effects of the ‘push–pull’ habitat management strategy: Parasitoid activity and soil fauna abundance Charles A.O. Midega a, b, * , Zeyaur R. Khan a , Johnnie Van den Berg c , Callistus K.P.O. Ogol d , Toby J. Bruce e , John A. Pickett e a International Centre of Insect Physiology and Ecology, Plant Health Division, P.O. Box 30772, Nairobi 00100, Kenya b Bioresource and Management Laboratory, Faculty of Agriculture, Kyushu University, Fukuoka, Japan c School of Environmental Sciences, North-West University (Potchefstroom Campus), Potchefstroom, South Africa d Department of Zoological Sciences, Kenyatta University, Nairobi, Kenya e Biological Chemistry Department, Rothamsted Research, Harpenden, Hertfordshire AL5 2JQ, UK article info Article history: Received 20 January 2009 Received in revised form 14 August 2009 Accepted 14 August 2009 Keywords: Collembola Abundance ‘Push–pull’ Stemborer Parasitism abstract We assessed the non-target effects of a habitat management system (‘push–pull’) on maize stemborer specialist natural enemy activity and soil Collembola. Two study sites in western Kenya were sampled. There were two treatments at each site, maize monocrop and ‘push–pull’. The latter comprised an intercrop of maize and Desmodium, Desmodium uncinatum Jacq., with Napier grass, Pennisetum purpur- eum (Schumach), as a trap crop planted around the edge of the plot (spaced 1 m from main crop). Tri- chogramma spp. were recovered from stemborer eggs while Cotesia sesamiae and Cotesia flavipes were recovered from stemborer larvae, and Dentichasmias busseolae from pupae. Mean number of eggs parasitized was significantly higher in the maize monocrop than in the ‘push–pull’ plots however proportions parasitized did not differ between the two systems. The number of larvae and pupae parasitized and dead from causes other than parasitism similarly did not differ between cropping systems. Proportions of larvae and pupae parasitized were significantly higher in the ‘push–pull’ than in the monocrop plots, indicating that the activity of larval and pupal parasitoids was enhanced. C. sesamiae female wasps were attracted to the volatiles from Desmodium flowers but not those from the leaves in a four-arm olfactometer bioassay. A total of 1530 individual Collembola in seven families were recovered from the plots. The ‘push-pull’ strategy did not have any significant effect on Collembola abundance and dominance. The factors underlying these observations and their implications are discussed. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Maize, Zea mays L., and sorghum, Sorghum bicolor Moench, production in sub-Saharan Africa is severely constrained by lepi- dopteran stemborers which cause yield losses of up to 80% (Kfir et al., 2002). The most important species in the region are Chilo partellus Swinhoe (Lepidoptera: Crambidae) and Busseola fusca Fu ¨ ller (Lepidoptera: Noctuidae) (Kfir et al., 2002). Most of the management strategies for these pests have had little impact (Van den Berg et al., 1998; Kfir et al., 2002). However, recently, a ‘push– pull’ habitat management system has been developed and disseminated against these pests (Cook et al., 2007; Hassanali et al., 2008; Khan et al., 2008a). The ‘push–pull’ technology, developed by the International Centre of Insect Physiology and Ecology (ICIPE) and its partners, is based on a stimulo-deterrent strategy where pests are repelled from a harvestable crop and subsequently trapped on an attractant plant (Miller and Cowles, 1991; Cook et al., 2007). In this system maize is intercropped with a leguminous fodder plant, Desmodium uncinatum Jacq., while Napier grass, Pennisetum purpureum Schumach, is planted around this intercrop. Desmodium has stem- borer moth repellent properties while Napier grass has attractant properties (Khan et al., 2000, 2006; Van den Berg, 2006; Khan et al., 2007). Desmodium thus repels gravid female moths (push) which are subsequently attracted to the Napier grass (pull) in a ‘push–pull’ strategy. The system is currently being used by >20,000 small- holder farmers in East Africa (Khan et al., 2009, in press). Effective control of stemborers has been achieved, with concomitant grain yield increases (Midega et al., 2005, 2006; Khan et al., 2008a). * Corresponding author. International Centre of Insect Physiology and Ecology, Plant Health Division, P.O. Box 30772, Nairobi 00100, Kenya. Tel.: þ254 59 22216/7/8; fax: þ254 59 22190. E-mail address: cmidega@mbita.mimcom.net (C.A.O. Midega). Contents lists available at ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro 0261-2194/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2009.08.005 Crop Protection 28 (2009) 1045–1051