ORIGINAL CONTRIBUTION Non-target effects of insecticides, entomopathogenic fungi and nematodes applied against western corn rootworm larvae in maize D. Babendreier 1,2 , P. Jeanneret 1 , C. Pilz 1,3 & S. Toepfer 4,5 1 Agroscope Reckenholz-T€ anikon Research Station ART, Z€ urich, Switzerland 2 CABI Europe-Switzerland, Delemont, Switzerland 3 Markt Hartmannsdorf, Austria 4 CABI, Hodmezovasarhely, Hungary 5 Chinese Ministry of Agriculture - CABI Joint Laboratory for Biosafety, Beijing, China Keywords biological control, Diabrotica virgifera, entomopathogenic fungi, entomopathogenic nematodes, neonicotinoid, pyrethroid Correspondence Dirk Babendreier (corresponding author), CABI Europe – Switzerland, Rue des Grillons 1, CH-2800 Del emont, Switzerland. E-mail: d.babendreier@cabi.org Received: October 29, 2014; accepted: March 24, 2015. doi: 10.1111/jen.12229 Manuscript is a contribution for the special issue from the IWGO Conference 2014. Abstract Field studies were conducted in southern Hungary over two field seasons to assess potential non-target effects of entomopathogenic nematodes (Heterorhabditis bacteriophora), entomopathogenic fungi (Metarhizium ani- sopliae), clothianidin-coated seeds and tefluthrin granules applied into the soil against larvae of the chrysomelid Diabrotica virgifera virgifera, one of the major North American and European maize pests. From field gauze cages set up over groups of maize plants, 1944 specimens of non-target ground-dwelling or emerging arthropods from 22 taxa were collected. The most abundant taxa belonged to the Diptera, Araneae and Hemiptera. Multivariate statistics revealed significant effects of soil conditions, year and treatments on non-target species composition. Soil parameters explained 10.5% of the overall variability in species composition. The application of biological control agents or insecticides for the control of Diabrotica larvae, together only slightly but significantly influenced non- target species composition, explaining 5.6% of the data variability. When pairwise comparisons were conducted, no significant effects on non-target compositions were detected for the entomopathogenic nematode, the en- tomopathogenic fungus, tefluthrin or clothianidin. However, clothianidin treatments tended to reduce densities of the beneficial arthropod taxa Coccinellidae, Hymenoptera, Araneae, and particularly Staphylinidae and Chrysopidae, whilst tefluthrin tended to reduce the Coleopteran families. No such trends were apparent for the two biological control agent treat- ments. Reasons for the small treatment effects on non-targets may be the generally poor arthropod diversity in soils of intensive field crops such as maize, as well as the application of all agents into relatively narrow soil areas close to maize plants. Introduction The western corn rootworm (Diabrotica virgifera virgifera LeConte, Coleoptera: Chrysomelidae) is considered to be one of the most serious pests of maize, Zea mays (L.), in North America (Levine and Oloumi 1991; Ward et al. 2005). Altogether, crop losses and countermeasures are estimated to cause annual costs of 1 billion US$ in North America alone (Chandler 2003), although even this impressive number may be an underestimate for today’s figures. Diabrotica v. virgifera was accidentally introduced from North America into Europe on several occasions between the 1980s and the early 2000s (Miller et al. 2005). Within 10 years, this pest species spread over J. Appl. Entomol. 139 (2015) 457–467 © 2015 Blackwell Verlag GmbH 457 J. Appl. Entomol.