Rootworms have developed resistance to genetically engineered corn

" We’re stuck with the potential risks to human health that may result from eating genetically-modified foods and we’re not even getting the promised benefits. In addition, American taxpayers could find themselves picking up the tab for any crop failures, thanks to government subsidies."

http://www.rawstory.com/rs/2012/07/08/rootworms-develop-resistance-to-genetically-engineered-corn/