One of the nation’s most widely planted crops - genetically engineered corn that makes its own insecticide - may be losing its effectiveness because a major pest appears to be developing resistance more quickly than scientists expected. [...] The hybrid was such a swift success that it and similar varieties now account for 65 percent of all U.S. corn acres - grain that ends up in thousands of everyday foods such as cereal, sweeteners and cooking oil.

But over the past few summers, rootworms have feasted on the roots of Bt corn in parts of four Midwestern states, suggesting that some of the insects are becoming resistant to the crop’s pest-fighting powers.