What about GMOs and weeds?
Pesticides are chemicals used to control "pests." Pests can refer to weeds, insects or diseases. Basically, pests encompass anything that threatens the healthy growth of a crop or has the potential to reduce the yield or quality of the crop. Controlling weeds is a big concern because weeds are the number one yield-robbing pest. That means that amongst the three types of pests described above, weeds are the biggest menace to harvesting a healthy, abundant crop.
To control weeds, farmers use herbicides. The use of herbicides, and other pesticides, is a source of concern for the public as trace amounts of these chemicals are often found to be present on the produce we buy at the grocery store.
Resistance to specific herbicides is one of the major traits introduced into genetically modified organisms, or GMOs. This has been done to provide new tools to manage and control weeds in fields of crop plants. Farmers can spray the whole field, but only the weeds will die. The crop will continue to grow without competition from weeds.
The most prevalent example of this herbicide resistance trait are crops that are resistant to glyphosate. Glyphosate is the most widely used herbicide in the world by volume, and is now used extensively in agriculture and can be found in many products used in the home garden. The use of these herbicide-resistant crops has allowed many farmers to switch from using other herbicides to glyphosate, which has a better environmental and safety profile than many other herbicides.
However, weeds adapt and evolve just like all other living species. They can develop a resistance to herbicides over time. Weeds that are resistant to glyphosate have emerged. These are often called ‘super weeds,’ although they are no different than any other weed. As a result of these adaptations, certain herbicide resistant crops that were initially very effective at controlling weeds in combination with glyphosate herbicide are no longer as useful as they once were.