Advisory letter on ‘The importance of maize and oilseed rape field margins for Lepidoptera’
Many of the genetically modified (GM) agricultural crops cultivated worldwide are insect-resistant. These crops, including maize, contain Bt toxins which are toxic to certain pest insects. Environmental risk assessments are part of applications for the cultivation of insect-resistant GM maize lines and must include the potential adverse effects of the crop on other organisms than the pest organisms (non-target organisms), such as Lepidoptera (butterflies and moths). The caterpillars of lepidopteran species that occur in maize field margins may be exposed to Bt toxins. If any of these species are susceptible to the Bt toxin concerned, this could lead to a decline in the size of lepidopteran populations.
COGEM has commissioned a research project to investigate the occurrence of lepidopteran species in maize field margins in the Netherlands. The results of this study show that lepidopteran species in the Netherlands occupy a broad habitat range and that these species do not depend for their survival solely on maize fields and field margins, where they could be exposed to Bt toxins. However, given the endangered status of lepidopteran species in the Netherlands, every increase in existing pressures could lead to a more rapid decline of lepidopteran populations.
COGEM has a strong preference for experimental and observational studies to assess the potential risks to non-target lepidopteran species. COGEM maintains that three lepidopteran species are the most suitable for use as representative species in laboratory experiments. COGEM advises the Minister for Infrastructure and Water Management to put this forward to the EFSA so that its guidelines may be amended accordingly.
The results of the study and the insights they give are important for improving the environmental risk assessment. COGEM points out that any future decision about the authorisation of a Bt crop should ideally include a comparison of the effects of the use of conventional and alternative methods of pest control on lepidopteran populations.