Weed of the Month: Giant Ragweed

  • giant ragweedCommon name: Giant ragweed
  • Scientific name: Ambrosia trifida1
  • Grass or broadleaf: Annual broadleaf
  • Giant ragweed grows in the Midwest and Eastern regions of the United States, but it is most heavily concentrated in the eastern Corn Belt states like Indiana and Illinois.2
  • Germination timing: Giant ragweed is traditionally an early season weed; however, its growing season is expanding. Giant ragweed typically sprouts in early May but has been seen as early as March. The weed can continue to cause issues through late July and can impede harvest if not controlled.2
  • Competitiveness: Giant ragweed is one of the most competitive weeds in corn and soybeans.
    • Two giant ragweed plants within a 110 square feet area can reduce corn yield by 13 percent.2
    • Soybean yield can be reduced by 50 percent when there is just one giant ragweed plant within a 110 square foot area.2
  • Giant ragweed can grow 1-5 feet taller than competing plants and can reach heights of up to 17 feet tall.2

Fast facts

  • When a giant ragweed plant first emerges, it can be identified by its spatulate cotyledons. These cotyledons are spoon-shaped and can range from 1 to 1 ¾ inches long.2
  • Giant ragweed always has three distinct lobes but can show up to five lobes that grow in an opposite arrangement.2
  • According to WeedScience.org, the first confirmation of herbicide resistant giant ragweed in the United States was in an Indiana soybean field in 1998.
  • Giant ragweed is a monoecious plant, which means that separate male and female flowers can found on a single plant.2
  • Giant ragweed seeds can be identified by their points and ridges that make them look like small crowns.2

Weed management tips2

  • Use multiple modes of action:
    • One of the best ways to fight giant ragweed is to use multiple modes of action in a herbicide program with both preemergence and postemergence herbicides.
  • Scout for weeds:
    • Look for giant ragweed two weeks after the postemergence herbicide application and determine if another application is needed.

Resistance Statistics*

  • According to to WeedScience.org, herbicide-resistant giant ragweed has been documented in corn and soybean fields in 13 states: Arkansas, Illinois, Indiana, Iowa, Kansas, Kentucky, Minnesota, Mississippi, Missouri, Nebraska, Ohio, Tennessee and Wisconsin.*

*Resistance confirmation does not include all weeds and may vary among different areas of each state.

Here are a few of the weed control solutions from Corteva Agriscience, Agriculture Division of DowDuPont:

Corn

DuPont Cinch® ATZ herbicide
Durango® DMA® herbicide
Elevore® herbicide
Enlist Duo® herbicide, as part of the Enlist weed control system
Enlist One herbicide, as part of the Enlist weed control system
Keystone® NXT herbicide
DuPont Realm® Q herbicide
Resicore® herbicide
SureStart® II herbicide
FulTime herbicide

Soybean

Durango® DMA® herbicide
Enlist Duo® herbicide, as part of the Enlist weed control system
Enlist One herbicide, as part of the Enlist weed control system
FirstRate® herbicide
Sonic® herbicide
DuPont Trivence® herbicide
DuPontEnlite® herbicide
DuPontAfforia® herbicide
DuPont™ FeXapan™ herbicide Plus VaporGrip® Technology

Additional information:

For more information, read these weed science resources:

Sources:
1University of Missouri Division of Plant Sciences 2018. Weed ID Guide, Giant Ragweed. https://weedid.missouri.edu/weedinfo.cfm?weed_id=18
2 University of Missouri 2014. Biology and Management of Giant Ragweed. https://weedscience.missouri.edu/publications/gwc-12.pdf

®™Trademark of The Dow Chemical Company (“Dow”) or E. I. du Pont de Nemours and Company (“DuPont”) or affiliated companies of Dow or DuPont. Cinch ATZ, FeXapan Plus VaporGrip Technology and Keystone NXT are federally Restricted Use Pesticides. Durango DMA, Elevore, EverpreX, FulTime NXT, Keystone NXT, Realm, Resicore, Sonic, SureStart II, Surveil and Trivence are not registered for sale or use in all states. FulTime NXT, Keystone LA NXT, Keystone NXT, Resicore and SureStart II are not available for sale, distribution or use in Nassau and Suffolk counties in the state of New York. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Enlist Duo and Enlist One herbicides are not registered for sale or use in all states or counties. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your area. Enlist Duo and Enlist One herbicides are the only 2,4-D products authorized for use in Enlist crops. DuPont™ FeXapan™ herbicide plus VaporGrip® Technology is a restricted-use pesticide. DuPont™ FeXapan™ herbicide plus VaporGrip® Technology is not registered for sale or use in all states. Contact your DuPont retailer or representative for details and availability in your state. IT IS A VIOLATION OF FEDERAL AND STATE LAW TO MAKE AN IN-CROP APPLICATION OF ANY DICAMBA HERBICIDE PRODUCT ON SOYBEANS WITH Roundup Ready 2 Xtend® technology, OR ANY OTHER PESTICIDE APPLICATION, UNLESS THE PRODUCT LABELING SPECIFICALLY AUTHORIZES THE USE. Contact the U.S. EPA and your state pesticide regulatory agency with any questions about the approval status of dicamba herbicide products for in-crop use with soybeans with Roundup Ready 2 Xtend® technology and follow all pesticide product labeling. Soybeans with Roundup Ready 2 Xtend® technology contain genes that confer tolerance to glyphosate and dicamba. Glyphosate herbicides will kill crops that are not tolerant to glyphosate. Dicamba will kill crops that are not tolerant to dicamba. Roundup Xtend® , VaporGrip® , Roundup Ready 2 Xtend® (Monsanto). VaporGrip® Technology is used under license from Monsanto Technology LLC. Always read and follow label directions. ©2018 Dow AgroSciences LLC