The indiscriminate use of “Bt” corn in the U.S. has strengthened rather than weakened the beetle it was supposed to fight, is the conclusion of a very large study published Feb. 27 in Science. According to scientists, the transgenic technology may soon prove obsolete. Until a decade ago, scholars had no doubts: the extension of Bt-corn fields in the U.S. led not only to an increase in crop yields, but also to a marked reduction in the need to use pesticides-even on neighboring land used for other crops-with an obvious saving in resources. But the new study, signed by 20 scientists from 18 global institutions, seems to dampen enthusiasm somewhat. Led by Ziwei Ye, a professor at Renmin University of China, the scholars examined data from 12 years of field trials in 10 Midwestern states of the so-called Corn Belt (“corn belt”). Their research shows that farmers are using too much Bt corn seed (engineered with insecticidal substances obtained from Bacillus thuringiensis to protect plants from pest attacks), resulting in the corn rootworm be etle(Diabrotica virgifera virgifera) to be combated developing resistance, undermining the effectiveness of the transgenic technology.