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Auchenorrhyncha (planthoppers and leafhoppers) are herbivorous organisms that can ingest Cry proteins from genetically engineered Bt-crops depending on their feeding behaviour. Consequently, they might be directly affected by non-target Bt-protein action and more importantly serve as a source of Cry protein exposure to beneficial predatory arthropods. During a three year field study, we surveyed the community of Auchenorrhyncha in Diabrotica-resistant Bt-maize DKc5143-Bt (event MON88017), its near-isogenic line and two conventional hybrids using sweep netting and custom made sticky traps. Zyginidia scutellaris (Herrich-Schäffer) (Hemiptera: Cicadellidae) represented more than 60% of all captured individuals, indicating that it is the dominant leafhopper within the maize community. The statistical analysis of Z. scutellaris data using confidence intervals for the ratios of mean abundance showed no consistent differences between the Bt-maize and the near-isogenic cultivar, indicating no negative impact of event MON88017. The two conventional hybrids Benicia and DK315 exhibited differences in terms of Z. scutellaris densities, which were greater than those observed between MON88017 and the near-isogenic line, but also not consistent over the years. Six more species accounted for an additional 39% of all captured specimens, while ten more species were found only as single individuals and can be considered vagrants from neighbouring habitats. These results inform future field work on the non-target impact of Bt-maize on this group of arthropods and monitoring approaches to assess biological control function by surveying herbivore communities.
Previous European guidance for environmental risk assessment of genetically
modified plants emphasized the concepts of statistical power but provided no
explicit requirements for the provision of statistical power analyses.
Similarly, whilst the need for good experimental designs was stressed, no
minimum guidelines were set for replication or sample sizes. Furthermore,
although substantial equivalence was stressed as central to risk assessment,
no means of quantification of this concept was given. This paper suggests
several ways in which existing guidance might be revised to address these
problems. One approach explored is the `bioequivalence' test, which has the
advantage that the error of most concern to the consumer may be set
relatively easily. Also, since the burden of proof is placed on the
experimenter, the test promotes high-quality, well-replicated experiments
with sufficient statistical power.
Other recommendations cover the specification of effect sizes, the choice of
appropriate comparators, the use of positive controls, meta-analyses,
multivariate analysis and diversity indices. Specific guidance is suggested
for experimental designs of field trials and their statistical analyses. A
checklist for experimental design is proposed to accompany all environmental
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