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Field Note: Common Ragweed Management

June 5, 2019 | Field Notes

Common Ragweed can be very competitive in no till situations due to its early season emergence. Many populations of Common Ragweed have developed resistance to Group 2 or ALS-inhibitor type herbicides such as Pursuit® or FirstRate®. There is also a population of Common Ragweed that is resistant to glyphosate.

Control in corn can come from use of a recommended rate of pre-emergence herbicide such as Keystone LA® or Surestart® II. In no till situations, an application of 2,4-D or dicamba can be helpful. Tillage is very effective against Common Ragweed as a control method. Post applications containing several modes of effective action is recommended by Farm Nutrients. Resicore® herbicide is extremely effective in post emergence control of Common Ragweed because it contains Stinger herbicide as one of its ingredients.

Soybean control can become slightly more difficult. PPO resistant populations of Common Ragweed have been found and glyphosate populations are becoming increasingly more common as well. As always, start clean with a tillage or burn down herbicide pass. Burn down herbicide options would be from the Group 4 family including 2,4-D and FeXapan® plus glyphosate. The combination of modes of action seems to be more effective than just using one of these burn down herbicides alone. If populations are not ALS resistant, an application of Sonic® or Authority First® can be effective residual control. Post emergence control of Common Ragweed is best when sprayed before weeds reach 4 to 6 inches tall. Glufosinate herbicides such as Liberty® can be effective in problem fields planted to LibertyLink® technology. Roundup Ready 2 Xtend® soybeans can be effectively sprayed with FeXapan® for control of Common Ragweed. Roundup Ready soybean systems and conventional systems offer the most difficult control of Common Ragweed. If populations are not ALS resistant, FirstRate® or Classic herbicides can be used for control of small weeds. If populations are ALS resistant, Flexstar®, Cobra®, or Ultra Blazer® herbicides offer the best control. As always, scouting and spraying weeds that are below 4 inches is the best method for clean soybean fields.