Alurking threat that has stymied US corn growers for decades is now returning to the forefront: western corn rootworm. Sometimes referred to as the "billion-dollar bug," the species' tiny larvae chew through the roots of corn plants, causing devastating yield losses. In 2003, farmers began planting a genetically engineered variety of corn known as "Bt," which produces a protein toxic to the pest species - but by 2009, the billion-dollar bug had already evolved adaptations for resistance to the toxin.
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