ORIGINAL CONTRIBUTION Impact of Cry1Ab toxin expression on the non-target insects dwelling on maize plants O. Habus ˇ tova ´ 1 , P. Dolez ˇal 1,2 , L. Spitzer 1,2 , Z. Svobodova ´ 1,2 , H. Hussein 1 & F. Sehnal 1,2 1 Biology Centre ASCR, Entomological Institute, C ˇ eske ´ Bude ˇ jovice, Czech Republic 2 Faculty of Science, University of South Bohemia, C ˇ eske ´ Bude ˇ jovice, Czech Republic Keywords aphids, environmental risk assessment, European corn borer, genetically modified crops, pirate bugs, thrips Correspondence Oxana Habus ˇ tova ´ (corresponding author), Biology Centre AS CR, Entomological Institute, Branis ˇ ovska ´ 31, 370 05 C ˇ eske ´ Bude ˇ jovice, Czech Republic. E-mail: habustova@entu.cas.cz Received: January 25, 2012; accepted: July 27, 2012. doi: 10.1111/jen.12004 Abstract The effect of transgenic maize MON810 (Bt maize) on the diversity and abundance of plant-dwelling insects was tested under field conditions in southern Bohemia (coordinates 48°N, 14ºE, 384 m a.s.l.) for three succes- sive years. The experiment was carried out on 10 0.5-ha plots of which five were seeded with the Bt maize and five with the non–Bt parental cul- tivar. The content of Bt toxin (Cry1Ab) was measured in plant tissues with a commercial ELISA kit. Randomly chosen plants (10 per plot) were taken from the field during the vegetation period in about 2-week intervals and thoroughly examined in the laboratory. Collected insects were identified and their counts were statistically analysed with CANOCO with respect to the Bt toxin, developmental stage of maize and the year of cultivation. No significant effect of Bt maize on the plant-dwelling non-target insects was detected. Correlation between the number of plants and detected insect diversity revealed that inspection of 20 plants (four per each of five plots) provided data reliable at 95% probability level; six plants per plot were sufficient for the analysis of aphids, thrips and Orius bugs. Introduction Insect pests are often the major cause of yield losses in agricultural crops. The most important pest of maize in Europe, the European corn borer, Ostrinia nubilalis (Hbn.) (Lepidoptera: Crambicidae), causes yield losses of 5–30% (Meissle et al. 2010). Pest management cur- rently relies on the applications of insecticides but their use often brings about ecological damage owing to lethality to the non-target species, insecticide accu- mulation in the soil, contamination of waters and sometimes the presence of insecticide residues in the harvested crops. Excessive use of insecticides may cause outbreaks of secondary pests by eliminating their natural enemies and altering trophic relation- ships in the ecosystem. In spite of this potential dan- ger, European corn borer is often controlled with broad-spectrum insecticides including pyrethroids and organophosphates that are cheap, suppress several arthropod pests simultaneously, and their use has a long tradition. The deployment of genetically modified (GM) crops, which express a toxin targeted to specific herbi- vores, is regarded as a suitable alternative to the pesti- cide use (Sharma et al. 2004; Romeis et al. 2006; Meissle et al. 2011). Evaluation of the risks and bene- fits of the GM crops has been in the focus of attention since their commercialization (Ferber 1999) but some concerns remain, particularly about possible environ- mental side effects (Firbank et al. 2005). In response to the fear of possible unwanted effect, EU authorities will demand post-market environmental monitoring (PMEM). We examined environmental impact of the GM maize event MON810 that was cultivated on the same plots for 3 years. Our data will be used in the development of PMEM methodology. MON810 maize has been genetically engineered to express the insecticidal protein Cry1Ab, one of the toxins produced by the bacterium Bacillus thuringien- sis. Different strains of B. thuringiensis produce differ- ent kinds of the Cry proteins, called Bt toxins, that act specifically against certain insect groups. Thus, it is © 2012 Blackwell Verlag, GmbH 1 J. Appl. Entomol.