A recent study analyzing over a decade of data from 10 U.S. Corn Belt states reveals that the overuse of genetically engineered corn designed to combat rootworm pests has led to economic losses for farmers. The research, led by Purdue University entomologist Christian Krupke and a team of 19 co-authors, highlights the unintended consequences of excessive reliance on transgenic corn hybrids that target rootworms. The study, published in Science, shows that pest pressures in many parts of the Corn Belt have significantly decreased since the introduction of rootworm-resistant corn, leading to a reduced need for broad deployment of these genetically engineered seeds.
The research revealed a fundamental difference between the eastern and western Corn Belt. In states such as Illinois, Iowa, and Nebraska, where corn is often planted continuously, rootworm pressures have remained high. In contrast, in states like Indiana, Ohio, and Michigan, where crop rotation is practiced, the need for rootworm-resistant hybrids has been lower. Despite this regional variation in pest pressure, the use of Bt corn corn genetically modified with the Bacillus thuringiensis (Bt) toxin has been nearly uniform across the region.
The study pointed out that while Bt corn helped to significantly reduce pest pressures after its introduction in 2003, the continued use of this technology has led to the development of resistance in rootworm populations. Scientists began observing resistance as early as 2009, raising concerns about the long-term viability of Bt corn as a solution to rootworm infestations. The research also highlighted the economic costs of using Bt hybrids, which include substantial technology fees for the seeds and the erosion of pest susceptibility over time. The continual use of Bt corn is likened to the gradual depletion of a finite resource each use reduces the effectiveness of the technology.
Farmers often select hybrid seeds that bundle multiple desirable traits, including resistance to rootworms, even when these traits may not be necessary for their specific conditions. This bundling, similar to traditional cable TV packages where consumers pay for channels they don’t watch, has led to excessive use of rootworm-resistant corn. This overuse has created a situation where the technology becomes less effective for everyone, as the development of resistance accelerates.
Experts, including Michigan State University entomologist Christina DiFonzo, argue that farmers need more flexibility in selecting traits for their seeds, akin to the on-demand services offered by streaming platforms. Such a “pick list” approach would help farmers use only the traits they need, reducing unnecessary reliance on rootworm-resistant corn and slowing the development of resistance. However, as DiFonzo points out, while money can be replenished, once the susceptibility of pests to Bt toxins is lost, the damage is irreversible.
The study also emphasized the importance of balancing the use of transgenic technologies with other pest management strategies. Researchers caution against returning to chemical insecticides, such as organophosphates or pyrethroids, which could harm beneficial organisms and soil ecosystems. Transgenic corn, with its environmental benefits, including reduced insecticide use, remains a crucial tool in feeding the growing global population and adapting to climate change.
Despite the resistance challenges, Krupke and his team argue that transgenic technologies like Bt corn are still valuable and should be managed carefully to ensure their long-term effectiveness. By reducing overuse and focusing on sustainable practices, farmers can help preserve the efficacy of rootworm-resistant corn and similar technologies for the future. This approach, researchers believe, will benefit both farmers and the broader agricultural system.
