Field Facts: Giant Ragweed
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Giant ragweed plants are notoriously difficult to control due to their growth rate and potential resistance to several herbicides, including glyphosate.
- Common name: Giant ragweed
- Scientific name: Ambrosia trifida
- Cotyledons: Round to oblong in shape with a purple stem
- Leaf shape: First pair of true leaves are unlobed and lance-shaped with toothed margins. Subsequent leaves are 3-lobed (occasionally 5-lobed) and lance-shaped with toothed margins.
- Stems: Single or branching and covered in short, rough hairs
- Flowers: Long, slim clusters of small, green flowers
- Reproduction: Monoecious (with male and female characteristics on one plant)
Fast facts
- Giant ragweed plants thrive in fertile soils and have a vigorous growth rate.
- One giant ragweed plant can produce about 5,500 seeds. The seeds are larger than those of other weeds, allowing the plants to emerge from deeper planting depths.
- Giant ragweed can reach up to 17 feet tall and is often 1 to 5 feet taller than the crop with which it is competing.1
- Competition from just two giant ragweed plants per 110 square feet throughout the growing season can reduce corn yield by 13%.
- Giant ragweed is even more competitive in soybeans than in corn. Just one plant per 110 square feet reduced yields by 50%.1
- According to WeedScience.org, 13 states have reported herbicide-resistant ragweed in various crops. The weed has shown resistance to glyphosate and ALS-inhibitor (Group 2) active ingredients.
Control tips
A weed control program with multiple modes of action can help control giant ragweed. A strong program should consist of a burndown or tillage, followed by preemergence and postemergence applications that include residual activity. When choosing solutions, keep in mind giant ragweed is resistant to glyphosate (Group 9) and Group 2 active ingredients.
- For corn, a preemergence application of SureStart® II herbicide followed by an early postemergence application of Resicore® XL herbicide can work against giant ragweed.
- For Enlist E3® soybeans, a program that starts with a preemergence application of Sonic® or Trivence® herbicide followed by Enlist One® or Enlist Duo® herbicide can control the weed.
- A preemergence application of Sonic® or Trivence® herbicides followed by a postemergence application of EverpreX® herbicide is another residual option that can be used with all soybean technologies.
- Crop rotation can help keep giant ragweed at bay. Michigan State University recommends including either forage or small grains in rotation. The weed can’t tolerate mowing, so forage is a good choice, and small grains can suppress giant ragweed.2
Consult your local Corteva Agriscience representative to identify which products and management practices will work best to control giant ragweed in your customers fields.
References:
1University of Missouri. 2014. Biology and Management of Giant Ragweed. https://weedscience.missouri.edu/publications/gwc-12.pdf
2Michigan State University. Giant ragweed. https://www.canr.msu.edu/weeds/extension/giant-ragweed
The transgenic soybean event in Enlist E3® soybeans is jointly developed and owned by Corteva Agriscience and M.S. Technologies L.L.C. 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 with Enlist® crops. Consult Enlist herbicide labels for weed species controlled. EverpreX®, Sonic®, Trivence®, Resicore® XL and SureStart® II are not registered for sale or use in all states. Resicore XL 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. Always read and follow label directions.