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Managing Marestail: How to Overcome the Troublesome Weed
Marestail is a notorious fall-emerging weed known for causing significant yield reduction in corn and soybean fields. An estimated one-quarter of all marestail seedlingsgerminate in the fall, survive through the winter and continue growing in the spring1. Though marestail is considered a winter annual, plants typically start flowering during the summer months1. This extended emergence period makes it difficult to manage the weed. Here is what farmers need to know about marestail and how to control it:
- Marestail can produce up to 200,000 seeds that are light and dispersed by the wind2.
- Even though farmers may not have a history of marestail in their fields, it can encroach onto their corn or soybean acres if the weed is in neighboring fields.
- The weed starts out as a small rosette, about 1 to 4 inches wide, and can be hidden under crop residue. Farmers should practice thorough scouting if they are concerned about marestail and look beneath debris to ensure fields are clean even after harvest.
- Because weeds are most vulnerable and easiest to manage when they are small, controlling marestail at the rosette stage is most effective.
Since the first confirmation of glyphosate-resistant marestail in Delaware in 2000, resistance has spread to fields in 26 other states, including many of the key corn- and soybean-growing states across the Midwest. Farmers can get the most up-to-date information about weed resistance from the International Herbicide-Resistant Weed Database.
To help combat the spread of weed resistance, farmers should consider a program approach that includes burndown applications, multiple passes, several modes of action and residual activity. Applying a burndown in fall or early spring can help farmers stay ahead of marestail before it grows large enough to steal resources from crops. It’s important to apply herbicides while weather conditions remain favorable - air temperatures above 50 degrees Fahrenheit and low winds.2 Elevore® herbicide provides excellent burndown control.
For corn, Resicore® herbicide fits perfectly in a preemergence application scenario, while Kyro® herbicide is a strong postemergence option. With soybeans, Elevore® herbicide is a good burndown choice. Farmers should consider Kyber Pro® herbicide as a preemergence selection. For Enlist E3® soybeans, apply Kyber Pro preemergence followed by Enlist One® herbicide as the foundational postemergence herbicide plus other qualified tank-mix partners.
For more information about weed resistance and a program approach to weed control, contact your local Corteva Agriscience representative.
1Jha, P., and R. Yadav. 2021. 2020 Summary of Herbicide Evaluations for Marestail (Horseweed) Control in Soybean. https://crops.extension.iastate.edu/cropnews/2021/02/2020-summary-herbicide-evaluations-marestail-horseweed-control-soybean
2Werle, R., C. Proctor, and J. Miller. 2016. Fall is Optimal for Marestail Management. https://cropwatch.unl.edu/2016/fall-optimal-marestail-management
The transgenic soybean event in Enlist E3® soybeans is jointly developed and owned by Corteva Agriscience and M.S. Technologies L.L.C. Following burndown, Enlist Duo® and Enlist One® herbicides with Colex-D® technology are the only herbicides containing 2,4-D that are authorized for preemergence and postemergence use with Enlist® crops. Consult Enlist® herbicide labels for weed species controlled. Enlist Duo and Enlist One herbicides are not registered for use or sale in all states and counties; are not registered in AK, CA, CT, HI, ID, MA, ME, MT, NH, NV, OR, RI, UT, VT, WA and WY; and have additional subcounty restrictions in AL, GA, TN and TX, while existing county restrictions still remain in FL. All users must check “Bulletins Live! Two” no earlier than six months before using Enlist One or Enlist Duo. To obtain “Bulletins,” consult epa.gov/espp/, call 1-844-447-3813, or email ESPP@epa.gov. You must use the “Bulletin” valid for the month and state and county in which Enlist One or Enlist Duo are being applied. Contact your state pesticide regulatory agency if you have questions about the registration status of Enlist® herbicides in your area. ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. IT IS A VIOLATION OF FEDERAL AND STATE LAW TO USE ANY PESTICIDE PRODUCT OTHER THAN IN ACCORDANCE WITH ITS LABELING. ONLY USE FORMULATIONS THAT ARE SPECIFICALLY LABELED FOR SUCH USE IN THE STATE OF APPLICATION. USE OF PESTICIDE PRODUCTS, INCLUDING, WITHOUT LIMITATION, 2,4-D-CONTAINING PRODUCTS NOT AUTHORIZED FOR USE WITH ENLIST CROPS, MAY RESULT IN OFF-TARGET DAMAGE TO SENSITIVE CROPS/AREAS AND/OR SUSCEPTIBLE PLANTS, IN ADDITION TO CIVIL AND/OR CRIMINAL PENALTIES. Additional product-specific stewardship requirements for Enlist crops, including the Enlist Product Use Guide, can be found at www.traitstewardship.com. Elevore®, Enversa™, Resicore®, Sonic® Boom and Kyro are not registered for sale or use in all states. Enversa, Resicore and Kyro 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.
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