One of industrial agriculture’s biggest GMO crops may have just backfired. Scientists have confirmed that corn-destroying rootworms have evolved to be resistant to the Bt corn engineered to kill them.

Bt stands for Bacillus thuringiensis, the name of the genetically modified corn’s ‘donor” organism. Bacillus thuringiensis is a naturally occurring soil bacterium that produces protein crystals that bind to certain receptors in the rootworm’s intestine, killing it. For years, farmers have planted Bt corn as an alternative to spraying insecticides. Bt corn accounted for three-quarters of all corn planting in 2013. That may have to change.

After finding a cornfield in Iowa in 2011 that was decimated by rootworm despite being planted with the Bt corn, Iowa State University entomologist Aaron Gassmann and his team began to study the pests’ interactions with the genetically modified organism (or GMO) corn in a lab. Their study, published Monday in the Proceedings of the National Academy of Sciences, describes the western corn rootworm’s rapid evolution after feeding on the engineered crop.

But Bt corn is still capable of warding off other pests, so farmers will likely keep planting it. Except now they’ll need to use pesticides to protect their crop from rootworms. As entomologists warned the […]