If you doubt this problem with BT GMO crops, check out this article
that references a research paper on Bt resistance in corn earworm. Granted this is a different crop and a different pest, but the mechanism is the same–the Cry proteins that eat up the intestines the larval stage of insects. Larvae becoming resistant to Cry proteins will make BT ineffective as pest control in corn, and will make use of BT on organic corn crops ineffective as well. The resistance in the GM crops is the result of conventional farmers not keeping a portion of their fields in non BT corn, and to be a haven for corn earworms without resistance to BT to survive and pass on their genes. If all the corn is BT the next generations will consist only of BT resistant earworms.
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