More pest insects due to transgenic soybeans

‘Benefits’ of genetically engineered plants completely reversed

3 June 2022 / In a recent publication, scientists from Argentina and Brazil show how the spread of black armyworm (Spodoptera cosmioides) is being promoted by the cultivation of transgenic soybean plants. Black armyworm are the larvae of a butterfly and considered to be a pest insect. Transgenic “Intacta” soybeans, which were originally produced by Monsanto, are resistant to glyphosate and produce an insecticidal protein. The combination of these traits contributes to the spread of the larvae which can then cause substantial damage in the fields.

The reason for this problem are unexpected interactions: the weeds are spreading in fields where transgenic soybeans are cultivated because they have become resistant to the herbicide glyphosate. These weedy plants serve as an excellent source of food for the larvae. In addition, the larvae feed on the transgenic soybeans despite the plants producing an insecticide. The toxin is not effective in the larvae and actually appears to increase their vitality, possibly because of ‘positive stress’, as the authors discuss. Consequently, the larvae are getting bigger and the number of offspring from the butterflies is higher. Both the insecticidal soybeans and the weeds which are promoted by the cultivation of the herbicide resistant soybeans seem to contribute to this effect.

This is not the first time it has been shown that the cultivation of transgenic plants can cause effects that are the exact opposite of those intended: there were reports as early as 2014, that “Intacta” soybeans appeared to promote the spread of larvae from another species (Spodoptera eridania, southern armyworm) feeding on the plants. Another scientific publication in 2021 showed that in Brazil, whiteflies (Bemisia tabaci) benefitted from the cultivation of genetically engineered soybeans. Whiteflies sucking the juices from the plants appeared to be more vital, and also have a significantly higher number of offspring.

A new aspect in the current study is the role of herbicide-resistant weeds in the spread of pest insects. The findings may help in understanding interactions between the genetically engineered soybeans and their environment that were not considered in the risk assessment. In this context, Testbiotech is demanding to give more weight to the precautionary principle. Genetically engineered plants should be subject to a comprehensive technology assessment, including a detailed examination of their claimed benefits.

Christoph Then,, Tel +49 15154638040