GMOs in agriculture are plants, animals, or microorganisms whose DNA has been changed in a lab using genetic engineering rather than traditional breeding. In practice, the term almost always refers to crops. Scientists identify a useful gene, such as one that provides insect resistance or drought tolerance, and transfer it into a plant’s genome to give it a new trait. The result is a crop that couldn’t have been created through conventional cross-pollination or selective breeding.
How GMO Crops Are Made
Traditional plant breeding works by crossing two related plants and hoping the offspring inherit desirable traits from both parents. It’s slow, imprecise, and limited to species that can interbreed. Genetic engineering bypasses those limitations. Scientists isolate a single beneficial gene, sometimes from a completely different organism, and insert it directly into a crop’s DNA. The insertion has historically been somewhat random in terms of where the new gene lands in the genome, but the trait it carries is highly specific.
The most common modifications fall into two categories: herbicide tolerance and insect resistance. Some varieties combine both traits in what the industry calls “stacked” seeds. Other engineered traits exist, including virus resistance, drought tolerance, and enhanced nutritional content, but herbicide tolerance and insect resistance dominate commercial agriculture.
The Major GMO Crops
Three crops account for the vast majority of genetically engineered acreage in the United States: corn, soybeans, and upland cotton. In 2025, 96 percent of U.S. soybean acres were planted with herbicide-tolerant varieties. For corn, 92 percent of acres used herbicide-tolerant seeds and 87 percent used insect-resistant seeds, with 84 percent planted as stacked varieties carrying both traits. Cotton follows a similar pattern, with 93 percent herbicide-tolerant and 91 percent insect-resistant.
Beyond those three, herbicide-tolerant seeds are widely used in alfalfa, canola, and sugar beets. Globally, biotech crop production covers roughly 206 million hectares. The United States leads with 74.4 million hectares, followed by Brazil (66.9 million), Argentina (23.1 million), India (12.1 million), and Canada (11.5 million). India’s entire biotech acreage is cotton, while Brazil and Argentina grow modified corn, soybeans, and cotton.
How Insect-Resistant Crops Work
Insect-resistant GMO crops carry a gene from a soil bacterium called Bacillus thuringiensis, which is why they’re often called Bt crops. This gene tells the plant to produce a specific protein that is toxic to certain insect pests, particularly caterpillars and beetle larvae.
The protein itself is harmless when it sits inside the plant tissue. When a target insect eats part of the plant, the protein enters its highly alkaline gut (pH 9 to 12), where digestive enzymes activate it. The activated protein binds to specific receptors on the insect’s intestinal cells, punches holes in the cell membranes, and causes the cells to rupture from the resulting fluid imbalance. The insect stops feeding and dies. Because the protein only activates under very specific gut conditions found in target insects, it doesn’t affect mammals, birds, or most other organisms that might eat the crop.
How Herbicide-Tolerant Crops Work
Most herbicide-tolerant crops are engineered to survive glyphosate, the active ingredient in Roundup. Glyphosate kills plants by blocking an enzyme they need to build essential amino acids. Without those amino acids, the plant can’t make proteins and dies.
Tolerant crops contain a gene from a soil bacterium that produces a slightly different version of that same enzyme. The bacterial version still does its normal job in the plant, helping it produce amino acids, but its shape prevents glyphosate from latching on effectively. The herbicide essentially slides off the modified enzyme while still binding to and disabling the natural version in weeds. This lets farmers spray an entire field with glyphosate, killing the weeds while the crop continues growing normally.
Impact on Pesticide Use
Over the 24-year period from 1996 to 2020, GMO adoption reduced total pesticide use by about 749 million kilograms of active ingredient, a 7.2 percent decrease. The environmental footprint of that pesticide use dropped even more, around 17.3 percent, because the chemicals that were eliminated tended to be more harmful than the ones that replaced them.
The picture differs sharply between insect-resistant and herbicide-tolerant crops. Insect-resistant technology has been a clear win for reducing chemical use. Bt cotton alone has cut global insecticide use on cotton by roughly 339 million kilograms, a 30 percent reduction. Bt corn has eliminated about 85 million kilograms of insecticide, a 41 percent cut. These crops essentially replaced chemical sprays with a protein produced inside the plant itself.
Herbicide-tolerant crops tell a more complicated story. In the early years, farmers used less herbicide overall because a single application of glyphosate replaced multiple passes with different chemicals. Over time, though, weeds evolved resistance to glyphosate, forcing farmers to spray more often and add additional herbicides back into the mix. Compared to the early 2000s, the total amount of herbicide used on tolerant crops has increased in most regions, and the environmental profile of those herbicides has worsened.
How GMOs Are Regulated in the U.S.
Three federal agencies share oversight of GMO crops under the Coordinated Framework for the Regulation of Biotechnology, established in 1986. The USDA’s Animal and Plant Health Inspection Service evaluates whether a new GMO plant could harm other plants or become an agricultural pest. The EPA regulates any pest-fighting substances the plant produces internally (like the Bt protein), as well as all pesticides used on both GMO and non-GMO crops. The FDA ensures that GMO foods meet the same safety standards as conventional foods for both human and animal consumption.
This means a single Bt corn variety, for example, goes through review by all three agencies before it reaches a farmer’s field. The USDA checks its potential impact on agriculture, the EPA evaluates the insecticidal protein it produces, and the FDA assesses whether the harvested grain is safe to eat.
Gene Editing vs. Traditional GMOs
A newer technology called CRISPR is reshaping the conversation about genetic modification in agriculture. Traditional genetic engineering inserts a gene from a different species into a crop’s genome. CRISPR works differently: it can make small, precise changes to a plant’s existing genes without adding any foreign DNA. Think of it as editing a sentence in a book rather than pasting in a paragraph from a different book.
This distinction matters for regulation. In the United States, the USDA has decided that CRISPR-edited crops with no foreign DNA are not regulated as GMOs, since the resulting plants could theoretically have developed the same changes through natural mutation. The European Union takes the opposite approach, treating all gene-edited crops as GMOs regardless of whether foreign DNA is involved. When CRISPR is used to insert a large gene from another species, however, the result is regulated as a GMO everywhere.
The practical difference is significant. A CRISPR-edited crop that simply tweaks an existing gene for better drought tolerance can reach the market in the U.S. without the years-long regulatory process that traditional GMOs require. This has opened the door for smaller companies and public universities to develop improved crop varieties, a space that has historically been dominated by a handful of large corporations because of the cost of regulatory approval.