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GE Brassica: Resistant Insects in a Few Years?

NZ’s Experimental GE Brassica Could Create Resistant Insects in Just a Few Years.

Scientists could spend 10 years developing GE Brassica vegetables that could create resistance in insects in just half that time, making them worse than useless.

The first documented field-evolution of caterpillars developing resistance to genetically engineered Bt (bacillus thuringiensis) plants has just been published. The bollworm (Helicoverpa zea), a devastating caterpillar for cotton and corn farmers has developed resistance in the field.

Previously there have been studies on laboratory resistance of Lepidoptera (caterpillars) to Bt but never before in the field. Professor Tabashnik- one of the scientists publishing the study- is quoted as saying “What we are seeing is evolution in action”.

The findings reflect warnings from independent scientists that Bt crops producing toxins all the time would destabilise insect populations in ways that occasional and infrequent use of Bt as a topical spray does not.

Bt has been used as a topical spray (Dipel) for the control of caterpillars on crops, especially by organic producers wanting to avoid toxic chemical insecticides. It is short acting and quickly breaks down in sunlight and rain. But in 1990 scientists isolated specific toxic ‘Cry’ genes from the Bt bacteria and spliced them into the DNA of seeds to create genetically engineered crops. These plants expressed the toxin in every cell throughout the life of the plant. .

Environmental conditions do not destroy the toxin, so Bt toxins from GE crops can also build up in the environment. Recent studies have found that the GE plant re locates the Bt toxin in different parts of the plant throughout its growing cycle; in early life the leaves, then in the bud/flower and at the end in the roots. The root exudates have been found to be persistent in soil for up to 2 years. In India, over the last three years there have been links to Bt cotton and livestock deaths after grazing the fields after harvest.

“The Bt toxin has been shown to affect human, animal health and the soil environment. Now we have clear evidence of the development of Bt insect resistance, meaning more pesticides or more toxic genes will have to be inserted to kill the resistant insects,” said Claire Bleakley of GE Free NZ in food and environment.

The findings cast further doubt on New Zealand Crop and Food’s 10 year field test of Bt Brassica (cauliflower, broccoli, cabbage and forage kale). The GE Brassica have been planted out even though the decision is under appeal in the High Court. The selected Brassica lines are genetically engineered with multiple copies of Cry genes and will only be expressing the highest levels of toxin.

“Crop and Food argued that resistance in insects has never been scientifically documented in the field and so ergo it would not occur. The latest evidence confirms that resistance will occur and their GE Brassica plants could create a pool of Bt resistant caterpillars in less time that they took to develop.”

“ERMA has allowed the Bt Brassica field test to proceed even though they are being legally challenged in the High Court. This new information shows the whole notion of the project is fundamentally flawed and that the expense of the field trials and the impending court case are a waste that should be avoided by ERMA cancelling the approval.”


References: First documented case of pest resistance to biotech cotton

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