New Zealand banned genetically modified (GM) crops from its shores two years ago. But a recent test there found 800 corn plants that were contaminated with either the YieldGard insect-resistant or LibertyLink herbicide-resistant genes. This particular batch of seed, which was imported from seed companies Monsanto and Garst, was supposed to have been free of genetically modified organisms. It's an example of how difficult it is keep track of GM crops. It also indicates that a zero tolerance policy for genetic contamination may be unattainable.

If there's a bright side to this story, it's that only 800 out of 1.8 million plants tested positive. That means contamination was extremely low. In fact, grain from those fields would likely qualify as organic under current U.S. organic standards. Nevertheless, officials say that grain from the contaminated crops, which were grown on New Zealand's North Island, was destroyed in August.