GM corn

February 27, 2025

Over-planting of GM corn costing farmers billions, study finds

By Douglas Main

A new study adds to evidence that farmers in the US corn belt have over-planted a type of genetically modified (GM) corn, leading to estimated losses of more than $1 billion as the pests the corn was designed to repel have grown resistant over time.

The authors of the paper, published Thursday in the journal Science, said their findings supported a move toward a “more diversified” seed supply.

Known as Bt corn because it contains up to five toxins produced by a bacterium called Bacillus thuringiensis, the specialty corn is designed to express proteins that make the plant toxic to certain pests, including corn rootworm. More than 85% of corn planted in the US is the Bt variety, to which various insect pests are becoming resistant.

After examining rootworm crop damage data from 10 states over the period 2005-2016, the researchers determined that many farmers planted more GM corn than was considered necessary to address pest problems. Bt seeds typically carry a significant price premium.

The scientists found that planting Bt corn in certain eastern Corn Belt states provided “only marginal yield protection benefits,” benefits that appear to often be eclipsed by the higher costs for GM seed versus non-GM seed.

December 23, 2024

Tribunal says Mexico violated trade agreement in banning GM corn

By Douglas Main

An international tribunal set up to resolve disputes between the United States, Mexico, and Canada has ruled that Mexico violated the terms of the international trade agreement in banning the import of genetically modified (GM) corn for human consumption.

The decision, handed down by a commission set up under the auspices of the US-Mexico-Canada Agreement (USMCA), was criticized by over a dozen civil and environmental groups, who argue that Mexico is well within its rights to restrict the import of this material for health precautions and others reasons.

Mexico has argued that it needs to ban GM corn to protect its citizens and the environment. Earlier this year, it filed a 189-page document with the tribunal outlining what it sees as the risks posed by GM corn and glyphosate.

“Mexico has legitimate concerns about the safety and innocuousness of genetically modified corn… and its indissoluble relationship with its technological package that includes glyphosate,” the Mexican government’s report states. There is “clear scientific evidence of the harmful effects of direct consumption of GM corn grain in corn flour, dough, tortilla and related products,” Mexico stated. More evidence is needed, Mexico says, to determine “whether and to what extent, such risks are transmitted to food products further downstream.”

The Mexican government said in a statement it would comply with the ruling. “The Government of Mexico does not share the panel’s determination, as it considers that the measures in question are in line with the principles of protection of public health and the rights of indigenous peoples, established in national legislation and in the international treaties to which it is a party.”

Genetically modified corn is used by most US growers; companies have engineered the crop to be toxic to certain insects and to tolerate being sprayed with certain herbicides. Corn, and products made with corn, have often been found to be contaminated with glyphosate, one of the active ingredients in Roundup weed killer, for instance, because farmers can spray the pesticide directly over the growing crop to kill surrounding weeds.

The U.S. has not done or commissioned the research necessary to really determine if GM corn has long-term effects on human health, said Chuck Benbrook, a long-time consultant and expert who worked with Friends of the Earth in defending the Mexican position. “The US government never did [an] appropriate risk assessment of GM corn, period,” he said.

May 3, 2024

US says Mexico ‘abandoned science’ in GM corn limitations

By Johnathan Hettinger

The United States has doubled down on allegations that Mexico is violating international trade rules by working to ban imports of genetically modified (GM) corn for human consumption, arguing in a filing made public this week that Mexico has “abandoned science” in expressing concerns about how GM corn impacts human and environmental health.

Mexico is violating its obligations under the United States-Mexico-Canada Agreement (USMCA), making “factual and legal errors” in attempting to justify its decision to ban GM corn for use in tortillas and and dough and to gradually move away from the use of GM corn in animal feed, the US said in its formal rebuttal to Mexico’s case.

The 120-page US response, filed with a tribunal charged with arbitrating the trade dispute, said that Mexico has not shown that GM corn is likely to harm humans or native Mexican varieties of corn that are not genetically modified as Mexico has feared.

The US filing comes in response to a 189-page report issued by Mexico explaining the risks it sees posed by GM corn.

For years, Mexico has allowed the import of GM corn in the country, but the administration of Mexican President Andres Manuel Lopez Obrador has taken aggressive moves against the import of GM corn and against the use of glyphosate weed killer in the country, citing concerns threats to the health of the Mexican population as well as to the health of the environment. Glyphosate is commonly used by US farmers in growing a wide range of crops, and is sprayed directly over the tops of growing corn and other crops that have been genetically engineered to withstand the weed killer. In addition to being genetically altered to withstand herbicides, GM corn has also been engineered to manufacture its own toxin to repel insects.

“Mexico has legitimate concerns about the safety and innocuousness of genetically modified corn… and its indissoluble relationship with its technological package that includes glyphosate,” the government’s report states. There is “clear scientific evidence of the harmful effects of direct consumption of GM corn grain in corn flour, dough, tortilla and related products,” Mexico stated. More evidence is needed, Mexico says, to determine “whether and to what extent, such risks are transmitted to food products further downstream…”