Farmers have overwhelmingly adopted genetically modified Bt corn to prevent rootworm infestations. This corn has been genetically modified to express insecticidal proteins derived from the bacterium Bacillus thuringiensis (Bt). This novel technology provides an efficient, effective, safe, and user-friendly alternative to labor-intensive pesticide applications. Unfortunately, the effectiveness of Bt corn is being undermined as rootworms evolve resistance to the technology. This resistance not only undermines the environmental efficiency of Bt corn but threatens many farmers’ profits by a considerable margin.
The efficacy of Bt corn, once as high as 92% in 2005, fell to just 80% by 2016. This increase is due to the relentless expansion of Bt corn and the rootworms’ increasing resistance to it. For the last 15 years, IRM reports have indicated that rootworms have grown resistant to Bt corn. Farmers across the Midwest are hurting, including those farmers who grow Bt corn at more-than-necessary levels. Farmers need to start implementing these tactics immediately. To ‘walk the talk’ on integrated pest management, they need to do more to raise non-Bt refuges to ensure this biotechnology remains effective.
Understanding Bt Corn and Rootworm Resistance
Bt corn has been trumpeted as a great success story in the field of agricultural biotechnology. The main Bt trait gives built-in protection against major insect pests, most notably rootworms. It does this by including proteins from Bacillus thuringiensis, a naturally occurring bacterium. This method reduces our reliance on chemical pesticides, providing a safer and scientifically proven pest control solution.
Yet the rapid proliferation of Bt corn hybrids has unintentionally ushered in the perfect storm for lowered technology effectiveness. Planting too much Bt corn for too long has given rootworms the chance to evolve resistance, eroding the built-in protection that Bt corn provides. As a result, farmers are experiencing reduced benefits from their investment in this technology.
Yet the emergence of this rootworm resistance phenomenon is hardly new. As we’ve been documenting for the last 15 years, that’s not a sustainable approach to pest management. The challenge lies in balancing the use of Bt corn with other strategies to mitigate resistance and preserve its efficacy.
Strategies for Managing Rootworm Resistance
As an answer to increasing rates of rootworm resistance, experts like Murdock encourage a more diverse management approach. One of these strategies is better crop rotation, which has been shown to control rootworm pressure more sustainably than just using more Bt corn. Farmers can break the rootworm life cycle by planting two different crops in succession. This practice contributes to decreasing rootworm populations and minimizing their effects on Bt corn fields.
Another important aspect of resistance management Non-Bt “refuges” are another key pillar of resistance management. These are small, specific areas within Bt ear corn fields where non-Bt crops are slotted in. These refuges stall the natural selection process. They protect the longterm utility of Bt corn by making certain that a percentage of rootworms remain vulnerable to its toxins.
The pyramid approach is another complementary, yet very promising strategy that entails changing the crops to express two or more distinct Bt toxins. This strategy is intended to slow rootworm’s natural selection process and extend the useful life of Bt traits.
Economic Implications and Future Prospects
These rootworm infestations have become a major cost driver for U.S. farmers. They incur high management costs and face reduced agricultural yields, resulting in an approximate $2 billion rippling loss annually. As the efficacy of Bt corn erodes thanks to widespread resistance, farmers are hit with a double whammy of added costs. This dire scenario exemplifies the immediate need to create sustainable pest management solutions that will protect our farmers’ harvests as well as their bottom lines.
One economic study from western states found the optimal adoption rate for Bt corn is 45% to as high as 75%+. This range maximizes both effectiveness and yield. Farmers need to pay close attention to these guidelines in order to prevent making resistance problems worse while continuing to enjoy the benefits of Bt technology. Farmers can help maximize the robustness of Bt traits by ensuring responsible use. This means enacting practices such as crop rotation, refuge building, and diversified management strategies to promote long-term agricultural sustainability.