Insects Developing Resistance to GM Bt Crops
April 3, 2012 GM Freeze today published a review of insect resistance to Bt toxins in GM maize and Bt cotton crops around the world. It shows how, contrary to promises from GM companies, pesticide use is increasing to keep up with insects in GM crops. [1]
Scientists have confirmed five incidents of insects evolving resistance to Bt toxins in the field to date: Bt cotton in India (2010) and US (2008), moth pests in maize in Puerto Rico (2007) and South Africa (2007) and a beetle pest in maize in the US (2011).
Reasons for resistance developing are:
*Failure to provide adequate non-GM refuges in GM crops to ensure non-resistant adult insects can survive to breed with resistant ones so that the resistance gene does not become dominant. Refuges are required by US laws that are widely flouted.
*Levels of Bt toxin in the crops too low to deliver lethal doses to pests. Sub-lethal doses mean resistance can develop as pests survive, mate and pass on the resistance gene. If the number of resistant individuals is high they can multiply quite rapidly and become dominant.
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