Field Note: Giant Ragweed Management

Corn:

Giant ragweed is best controlled with full rates of herbicide early in its growth. Size matters, just like Common Waterhemp or Palmer Amaranth. In corn, start with a clean seed bed by either using tillage or a burn down application of 2, 4-D or dicamba with a residual herbicide. Farm Nutrients recommends an application of either Acuron® or Resicore® herbicide for best control and residual options either pre-emerge or post emerge. Status herbicide can be utilized as well.

Soybeans:

With soybeans, options become limited. Giant Ragweed grows very quickly and can easily get ahead of soybeans if not controlled early when it is small. In tilled fields, tillage will help do the trick to remove small seedlings then a treatment with Authority First® or Sonic® herbicide for residual. In no-till situations, an application of 2,4-D or FeXapan® herbicide in RR2 Xtend® soybeans is recommended. Farm Nutrients also recommends the addition of a residual herbicide to these burn down applications such as Authority First®, Sonic®, or Enlite®.

Post emergence options for giant ragweed in Roundup Ready® soybeans are limited. Several giant ragweed populations have become glyphosate resistant. The use of PPO herbicides, such as Flexstar® or Cobra, are relatively effective. However, where ALS resistant populations of giant ragweed have not developed, FirstRate® herbicide is a good option for control.

LibertyLink® herbicide systems provide a great option for control of problem populations of
giant ragweed with the use of glufosinate herbicide. Be sure to use plenty of water and appropriate rates. Currently, the best option we have found for fields with resistant giant ragweed populations is to utilize the RR2 Xtend® soybean system and FeXapan® herbicide.

For questions or concerns, contact your local Farm Nutrients representative or call the agronomy center at 712-286-5700.