Journal or Publishing Institution: Bundesministerium für Gesundheit und Frauen
Author(s): Dolezel, M., Heissenberger, A. and Gaugitsch, H.
Article Type: Journal Publication
Record ID: 524
Abstract: This review evaluates scientific studies published in peer-review journals during the last 3-4 years that considered ecological effects of insect resistant (Bt) and herbicide tolerant maize. The majority of the scientific studies deal with ecological effects of maize containing the Cry1Ab toxin. In contrast, very few studies are available that considered other Cry toxins used in Bt maize such as Cry3Bb1 or Cry1F. Studies dealing with the Cry1Ab toxin relate to effects on non-target Lepidoptera which were the first non-target effects confirmed for Bt176 maize. New studies confirm these adverse effects of Bt176 pollen to non-target Lepidoptera but show that also MON810 and Bt11 maize pollen or anthers may adversely affect lepidopteran larvae especially under prolonged exposure. Additive effects can be expected when larvae are exposed to a combination of Bt pollen and anthers containing the Cry1Ab toxin. Generally, effects on lepidopteran larvae are shown to be species and age-specific. Exposure of non-target lepidopteran larvae to Bt maize pollen under field conditions can be highly variable and is still unknown for the majority of European butterfly species. Published studies on ecological effects of Bt maize containing the Cry1Ab toxin also deal with impacts on other non-target organisms than Lepidoptera, such as herbivorous and predatory arthropods. A large range of herbivorous or predatory species have been shown to contain the Cry1Ab toxin when exposed to Bt maize in the field and adverse impacts on some species were confirmed mostly in laboratory studies. There is a definite need for standardization of laboratory feeding assays or tritrophic experiments with non-target herbivores and predators in order to enable the comparability of these studies. It is unclear if these adverse effects which were observed in the laboratory can be also translated to field conditions. Results on nontarget arthropod abundance in Bt and non-Bt maize fields are inconsistent and adverse effects are mostly restricted to single years or locations or certain species. Methodological flaws in the experimental design and few replications make it unlikely to detect small abundance effects of these non-target organisms in most field studies. According to the studies currently available major effects on non-target species abundance due to Bt maize cultivation seem to be rather unlikely. Therefore the emphasis of further studies should be on the detection of subtle and long-term effects to non-target organisms. Adverse effects of Bt maize containing the Cry1Ab toxin on parasitoids and hyperparasitoids have been shown and are most likely due to indirect and host-mediated effects. Reports on soil persistence and insecticidal activity of Cry1Ab toxins are still controversial although differences in the experimental design or methods used explain to some extent the different results obtained. Some adverse effects of Bt maize on different soil organisms are indicated but confirmation of these indications is still needed. Nevertheless decomposition is most likely different between Bt and non-Bt maize containing the Cry1Ab toxin and was confirmed even for different Bt plant species which is probably the result of differences in lignification patterns between Bt and non-Bt
maize. In contrast to non-target studies of Bt maize containing the Cry1Ab toxin only few studies have so far evaluated in depth non-target effects of the Cry3Bb1 containing maize. These studies give only few indications for consistent or major effects of this toxin on non-target organisms. Neither laboratory studies nor field experiments considering effects of the Cry1F toxin or the insecticidal toxins Cry34Ab1 and Cry35Ab1 on non-target herbivores, predators or soil organisms are so far available. Currently no evidence is available confirming negative impacts of Cry1Ab, Cry3Bb1 and Cry1F toxins on pollinators such as honey bees.
Only few studies are currently available that consider ecological effects of herbicide tolerant maize. The results of the British Farm Scale Evaluations were re-analysed recently. Exclusion of pre-emergence atrazine treatments from the analyses resulted in fewer positive effects of the herbicide tolerant maize fields compared to the non transgenic maize fields than reported previously both for weeds and arthropods. Other studies have, however, shown that the continuous use of glyphosate can change weed communities. Other studies considering herbicide tolerant maize predict the increase of infections by root pathogens due to the delay of the herbicide application. The occurrence of herbicide tolerant weeds has been observed since the large-scale introduction of herbicide tolerant crops and a further increase in abundance and frequency of herbicide resistant weeds is expected to occur.
Keywords: insect resistant maize, herbicide tolerant maize, Bt maize, Cry1Ab, Cry3Bb1, Cry1F, MON810, Bt176
Citation: Dolezel, M., Heissenberger, A. and Gaugitsch, H., 2005. Ecological effects of genetically modified maize with insect resistance and/or herbicide tolerance. Bundesministerium für Gesundheit und Frauen, Forschungsberichte der Sektion IV, 6, p.64.
