A new study from Michigan State University reveals a costly truth: overplanting genetically modified Bt corn in the eastern U.S. is accelerating insect resistance—and hurting farmers’ wallets in the process.
Key Points at a Glance
- Overuse of Bt corn in eastern U.S. states is reducing its effectiveness against corn rootworm
- Eastern regions have less rootworm pressure but still plant expensive Bt varieties
- Resistance in rootworms is evolving faster due to unnecessary exposure to Bt proteins
- MSU study suggests targeted Bt use could save nearly $2 billion in long-term costs
- Call for better farmer communication and broader seed options
Field corn, a staple of the American agricultural landscape, is facing an ironic threat—not from pests alone, but from the very biotech solution meant to protect it. A comprehensive study led by Michigan State University has found that the widespread overuse of genetically modified Bt corn, especially in eastern Corn Belt states, may be inadvertently helping the corn rootworm develop resistance faster than ever.
Bacillus thuringiensis, or Bt, is a soil bacterium whose genes have been harnessed to produce corn that naturally fends off pests like the notorious corn rootworm. But as MSU professor Felicia Wu explains, the rootworm—dubbed the “Loki” of agricultural pests—continues to evolve around every obstacle placed in its path, including Bt corn. This evolutionary resilience is being fueled, in part, by unnecessary Bt planting in regions where the pest is not even a serious concern.
“The more you plant it, the faster it breaks,” Wu said. In eastern states like Ohio, Michigan, and Pennsylvania, farmers are often planting expensive Bt-protected corn even though corn rootworm pressure is minimal. In contrast, major corn producers like Iowa and Nebraska have far more significant pest issues, making Bt corn much more necessary.
Why does this matter? Because every time a pest is exposed to a pesticide—or a built-in genetic trait like Bt—it gets an opportunity to adapt. Insects that survive become the basis of new, resistant populations. The study highlights a phenomenon well known in agriculture: excessive use of a single control method inevitably leads to resistance.
The financial toll is staggering. Bt seeds cost more due to the layered protection traits they carry. Yet farmers in low-risk regions are spending more for protection they don’t need. MSU researchers estimate that reducing Bt planting rates from 50% to just 18% in the eastern Corn Belt could have saved nearly $100 million in one year—and a projected $1.98 billion over time.
Wu and her team call for a smarter, more localized approach to Bt corn deployment. That includes offering more seed options that do not contain rootworm-targeting traits, and improving communication with farmers about pest risks and economic thresholds. Simply put, it’s about using the right tool for the right job—and not overusing it.
Without change, the long-term effectiveness of Bt corn could be compromised across the entire U.S., as resistance continues to spread. “If we keep using corn rootworm-protected Bt varieties in places where they’re not needed, we’re only speeding up the time before this biotech solution fails everyone,” Wu warned.
The findings published in the journal Science and supported in part by the U.S. Department of Agriculture suggest an urgent need to rethink pest management strategies. While genetically modified crops have transformed modern agriculture, their future depends on responsible stewardship. Bt corn may be powerful—but even powerful tools need to be used wisely.
Source: Michigan State University
