Aug 2, 2005

Research Projects

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Toxicity of Bt maize for parasitic waps

(2001 – 2004) Federal Biological Research Centre for Agriculture and Forestry (BBA), Institute for Biological Control; Darmstadt

Topic

The focus of the research project is on the protection of beneficial insects in agriculture.

• Are beneficial parasitic wasps (_Trichogramma_) – the natural antagonists of the European corn borer – affected by pollen from Bt maize?

The project investigated only Trichogramma parasitic wasps. Trichogramma species are very sensitive and are used as indicator organisms for the official testing of pesticides. The results can therefore generally be applied to other parasitic wasps. However, in individual cases separate testing of other parasitic wasp species is recommended for transgenic plants.

Summary

The project was abandoned in 2003 because no effects of the two Bt maize strains could be found on the parasitic wasps. This meant that planned outdoor experiments were abandoned. Experiments in Italy on outdoor Bt maize confirm the available laboratory results: the Italian experiments did not find any difference between parasitization of European corn borer egg batches in Bt maize and isogenic maize either. According to available results, Bt maize food sources produced no negative effects on the life data or activity of Trichogramma parasitic wasps.

Experiment description

Feeding experiments in the laboratory. The impacts of Bt maize as a food for particular parasitic wasps were investigated. To test the impacts, feeding experiments were carried out in the laboratory.

Food sources were pollen and plant sap, but also honeydew, which is excreted by the aphids. These various food sources from Bt maize of the Mon810 and Bt176 strains were used and compared with isogenic maize strains.

As well as the direct toxicity on the adult parasitic wasps, the effects on egg laying, foraging (host finding) and lifespan and development duration of the offspring were also of interest.

Results

Feeding experiments in the laboratory. No influence of the Bt pollen was observed on the predator wasps even after seven generations.

Unlike sap, pollen plays a certain role as a food source for the parasitic wasps, although they prefer honeydew. More recent investigations by other research groups show that the phloem sap from the plant’s nutrient vessels does not contain Bt toxin and that aphids were not harmed. This was supported by the current project, in which honeydew from aphids was not found to have any negative effects on the parasitic wasps.

Experiments were carried out in small cages and voleries, in which the parasitic wasps parasitized European corn borer eggs after being fed on pollen or on pollen and leaves of Bt maize. No differences were found in the parasitization and lifespan. The results of the investigation into toxic effects of various plant parts of Bt maize on Trichogramma showed no significant negative effects on Trichogramma parasitic wasps.