Field trials for assessing risks of GM maize on non-target arthropods in Europe:the Spanish experience

Abstract: Field trials may be required to assess risks of genetically modified (GM) crops for non-target arthropods (NTAs). In this work we summarize some published data and conclusions of 20 field trials conducted in Spain from 1998 to 2010 to assess risks of Bacillus thuringiensis (Bt) and herbicide-tolerant (HT) maize. Most abundant herbivores, predators, parasitoids and detritivores observed in visual sampling and caught in pitfall and yellow sticky traps were statistically analyzed with conventional ANOVA and also with meta-analysis. Main conclusions are: (i) In general, no effects of different Bt traits on non-target arthropods in maize were found in the field, (ii) The former conclusions were confirmed by a meta-analysis approach of the field data that allowed improving drastically statistical power and, therefore, effect detection capacity, (iii) there are a number of representative taxa that should be preferably recorded to achieve an acceptable level of statistical power, (iv) as abundance was the main factor determining effect detection capacity, a minimal value of arthropod abundance may be used to select indicator species for measuring effects of GM maize on NTAs, and (v) other field trial characteristics may reduce considerably the critical value of mean abundance necessary to achieve acceptable levels of effect detection capacity. Some of these conclusions could be reached by theoretical considerations and simulation studies but the fact that they are validated by real field data enhances their value for practical guidance on how environmental risk assessment (ERA) studies may be conducted.