This website was created for Biology 361: Genetically Modified Organisms at Davidson College.by Mike Chase and Monica Siegenthaler
|Many crops and weeds have created a tolerance to herbicides by prevention of translocation and/or absorption into the cells. Resistance selected for when a common mode of action is used repeatedly over crop seasons. Weeds that are susceptible to that herbicide will decrease in numbers from year to year, allowing other weeds that are resistance to the herbicide to establish themselves in the crop fields. If the same mode of action herbicide is used each year, then there is no disruption of the reproductive cycle of the resistant weed, resulting in a continually growing population of the resistant weed (Gunsolus, 2002).||
Monsanto's "Roundup Ready" soybeans are engineered
to resist the widely used herbicide Roundup. Crops survive in fields
sprayed with Roundup, but weeds are killed. Photo: Courtesy of Monsanto.
Permission pending from http://www.npr.org/programs/morning/features/2001/nov/biotech/011115.crops.html
Prevention of Weed Resistance
To prevent a weed from becoming resistant to the current herbicides used, farmers must follow three techniques:
The cultivation or herbicidal treatments of post-emergent weeds are also possible solutions to controlling resistant weeds. The cultivation of weeds before they go to seed will greatly reduce the spreading of certain species of weeds (Future Trends In Weed Managment, 2002).
|Resistance to Glyphosate
Glyphosate (roundup) is the world’s most commonly used herbicide. Monsanto, the biotech creator of Glyphosate, claims the use of glyphosate-resistant crops will reduce the use of normal toxic herbicides. It is argued that in the long run, other factors will play into the total chemical use in the future. Other considerations that must be accounted for included: