Weed Resistance Management
Farmers have been dealing with the issue of herbicide-resistant weeds since the 1950s, and it is a simple fact that growers use multiple methods to control weeds, including herbicides, tillage and mechanical weed removal. Resistance is a herbicide issue. It is not directly related to biotech-enhanced crops and includes herbicides beyond glyphosate, the active ingredient in Roundup® agricultural herbicides.
Growers are currently battling weeds resistant to some commonly used broadleaf herbicides which are the foundation of current weed control programs for sugar beets. Roundup Ready® sugarbeets give them a new tool to successfully and responsibly control these and other weeds. There are no crop rotation restrictions for Roundup agricultural herbicides offering additional crop rotation options to sugar beet growers.
History demonstrates that growers continue to grow and manage their crops even after the occurrence of weed resistance, and that the affected herbicide products continue to be valuable and important.
Worldwide, there are 13 weed species with biotypes confirmed to be resistant to glyphosate, according to the official listing in the International Survey of Herbicide Resistant Weeds available at www.weedscience.org. Nine of these resistant biotypes are found in the United States. Some are found in areas where Roundup Ready crops are not grown. Roundup agricultural herbicides continue to be the cornerstone for weed management programs in Roundup Ready crops.
Glyphosate-resistant weeds found in the United States in areas where Roundup Ready crops are grown:
- Palmer amaranth (Palmer pigweed)
Georgia, Tennessee, Arkansas
- Common ragweed
Arkansas, Missouri, Kansas
- Marestail (Horseweed)
Arkansas, California, Delaware, Kansas, Kentucky, Illinois, Indiana, Maryland, Michigan, Missouri, Mississippi, Nebraska, North Carolina, New Jersey, Ohio, Pennsylvania, Tennessee
Missouri, Illinois, Kansas, Minnesota
- Giant ragweed
Indiana, Ohio, Arkansas, Minnesota, Kansas, Tennessee
- Italian Ryegrass
Mississippi, Oregon (Orchard)
Note: California, Minnesota, Michigan and Nebraska are the four states where sugar beets are grown and where glyphosate-resistant weeds have been found.
Weeds found to have glyphosate-resistant populations not in Roundup Ready crops in the United States are:
- Rigid Ryegrass
California (discovered in almonds)
- Hairy Fleabane
Monsanto, the maker of Roundup agricultural herbicides, takes product stewardship and claims of resistance to glyphosate very seriously. Monsanto continually evaluates its recommendations for weed control and provides alternate weed control recommendations for any biotype confirmed as resistant. When glyphosate-resistant weed biotypes have been identified, they have been effectively managed with other herbicides and/or cultural practices.
Monsanto is committed to working with growers to address weed resistance to glyphosate. Monsanto encourages growers to report incidents of repeated non-performance of a Monsanto-branded herbicide to their local Monsanto retailer or to call 1-800-ROUNDUP. Monsanto investigates and addresses potential resistance, and implements control recommendations where resistance is observed.
Weed Resistance Management Resources
Monsanto’s educational weed resistance management Web site provides its customers comprehensive and timely information on weed control strategies for Roundup Ready cropping systems. Weed Resistance Management tools are available online. The site includes reference materials and other items designed to help crop producers and crop advisors steward herbicides and manage weed resistance. Fact sheets detailing practical management tactics for hard-to-control weeds are available online. In addition, Monsanto hosts a risk evaluation tool for growers in corn-soybean rotation, at www.weedtool.com. This tool provides best practices to reduce the risk on a field by field basis.
Monsanto Technology Use Guide (TUG)
All growers of Roundup Ready crops receive a Monsanto TUG, which includes weed resistance management information, as well as specific application guidelines by crop. A copy of the current TUG is available by calling 1-800-ROUNDUP. The weed resistance management guidelines can be found online at http://www.weedresistancemanagement.com.
International Survey of Herbicide-resistant Weeds
A comprehensive listing of herbicide-resistant weeds worldwide, the survey is a searchable database of resistant weeds by species, location and herbicide mode of action.
Online Weed Resistance E-Learning Courses
These computer-based training modules educate growers and agriculture industry professionals on how to reduce the potential development of resistant weeds
Sugar Industry Biotech Council – http://www.sugarindustrybiotechcouncil.org/learning-module/index.htm
Other sites offering E-Learning Courses include:
National Corn Growers Association – http://www.ncga.com
American Soybean Association – http://www.soygrowers.com/members/WRM/
National Cotton Council – http://www.cotton.org/tech/pest/wrm/
National Association of Wheat Growers – http://www.wheatworld.org/
American Sugar Beet Growers Association – http://www.americansugarbeet.org/
U.S. Canola Association – http://www.uscanola.com/
Beet Sugar Development Foundation – http://www.bsdf-assbt.org/index.htm
2008 Weed Resistance Management General Recommendations
Monsanto recommends the following general guidelines for minimizing the risk of weed resistance:
- Scout your fields before and after herbicide application.
- Start with a clean field, using either a burndown herbicide application or tillage.
- Control weeds early when they are small.
- Add other herbicides (e.g. a selective and/or a residual herbicide) and cultural practices (e.g. tillage or crop rotation) as part of your Roundup Ready cropping system where appropriate.
- One method for adding other herbicides into a continuous Roundup Ready system is to rotate to other Roundup Ready crops.
- Use the right herbicide product at the right rate and the right time.
- Control weed escapes and prevent weeds from setting seeds.
- Clean equipment before moving from field to field to minimize spread of weed seed.
- Use new commercial seed as free from weed seed as possible.