Assessing the impact of insecticidal GM crops on non-target arthropods -- the importance of laboratory study design

One of the concerns related to the environmental release of insecticidal genetically engineered (GE) crops is their potential adverse impact on valued non-target arthropods such as natural enemies. This risk is thus assessed prior to the commercial release of a novel GE crop. A typical risk hypothesis related to non-target effects of insecticidal GE plants is that the expressed protein is not toxic to non-target organisms at the concentration present in the field. Typically, the risk assessment follows a tiered approach that starts with laboratory studies under worst-case exposure conditions since such studies have a high ability of detecting adverse effects on non-target species, if present. Laboratory studies are thus a powerful tool to study the GE crop effects on non-target organisms. However, a number of design criteria should be followed to ensure hat the studies conducted are reproducible, test clearly defined hypotheses, and reveal interpretable results. These properties contribute to the robustness of the study and confidence in the results. The most important laboratory study design criteria will be presented and discussed using examples from our own research with Bt-transgenic crops and predatory arthropods.