Tips for Managing Weed Resistance

In the fall, growers can scout their fields from the combine cab, taking note of weed escapes and yield inconsistencies. Information, such as field conditions, crop health and yield data, will help with next year’s management decisions. For example, if there are noticeable patterns where weed escapes occur, you can help your customers update their weed resistance management plans for next year.

Since Roundup Ready® crops were introduced, the technology has become the farm industry standard. But using glyphosate as the primary, or only, herbicide mode of action has resulted in an increase in glyphosate-resistant weeds. These include waterhemp, marestail, Palmer amaranth and giant ragweed, among several others.

“The glyphosate-resistant weeds are becoming more of a problem each and every year,” says Pat Ross, grower research plot participant from Lawrence, Kansas. “We’re having real trouble with marestail, and beginning to see resistance with Palmer amaranth. It just seems like there’s always a problem out there.”

To help you and your customers manage hard-to-control and resistant weeds, Dow AgroSciences has developed the Enlist™ Weed Control System, a new herbicide-tolerant trait technology. Following regulatory approvals, Dow AgroSciences recommends using the Enlist system as part of an integrated weed management program.


Management is key to controlling resistant weeds. There are three major steps to remember.

1) Follow a herbicide program approach that includes multiple modes of action.
2) Make timely herbicide applications.
3) Scout fields before and after applications.

One of the most important aspects of a program approach is to use multiple modes of action. That’s essential to preventing increases in resistant weed populations. In addition to aiding in the prevention of resistant weeds, residual herbicides also help maximize yield potential by controlling weeds that can rob nutrients from the crop early in the season.

Dow AgroSciences will recommend the use of a program approach, including a preemergence herbicide, such as SureStart® II herbicide for corn and Sonic® herbicide in soybeans, followed by a postemergence application of Enlist Duo™ herbicide. This recommended best management practice incorporates different modes of action and will help sustain the Enlist system for the long term.

“We use a preemergence herbicide followed by a postemergence herbicide on all of our corn acres,” says Mark Jagels, grower research plot participant from Davenport, Nebraska. “I’m interested in Enlist Duo because it provides our corn crop with another mode of action to manage and prevent weed resistance.”

Herbicides work best when applied at the recommended rate and timing. When working with your customers to develop management plans, be sure to consider weed height, growth stage and environmental conditions. Refer to product labels for more information.

It’s important to regularly scout fields throughout the season. Keep an eye out for noticeable patterns where weed escapes occur. Resistant weeds will often first appear as patches in fields. Identifying these patches early helps prevent widespread distribution of the resistant population.

Also, if weeds are present, it could be an indication of a plugged nozzle on the sprayer or that an incorrect herbicide rate was used. However, if live weeds are next to dead weeds, and they appear to have been about the same size, the live weeds may indicate there is a population of resistant weeds growing in the field.

An effective weed resistance management program includes following a program approach with multiple modes of action, timely application of herbicides and scouting fields. The Enlist™ Weed Control System represents the next step forward into the modern era of farming.

Pending regulatory approvals, Dow AgroSciences expects to launch Enlist™ corn and soybeans in 2015, followed by Enlist E3™ soybeans and Enlist cotton in 2016.

For more information, visit and follow @EnlistOnline on Twitter.

®™DOW Diamond, Colex-D, DMA, Duramax, Durango, Enlist, Enlist Duo, Enlist E3, FulTime, Instinct, Keystone, N-Serve, Sonic, SureStart, Surpass and Surveil are trademarks of The Dow Chemical Company (“Dow”) or an affiliated company of Dow. ®Roundup Ready is a registered trademark of Monsanto Technology LLC. Always follow IRM, grain marketing and all other stewardship practices and pesticide label directions. Roundup Ready® crops contain genes that confer tolerance to glyphosate herbicides. Glyphosate herbicides will kill crops that are not tolerant to glyphosate. B.t. products may not yet be registered in all states. Check with your seed representative for the registration status in your state. FulTime NXT, Keystone LA NXT and Keystone NXT are federally Restricted Use Pesticides. Duramax, Durango DMA, FulTime NXT, Instinct II, Keystone LA NXT, Keystone NXT, Sonic, SureStart II, Surpass NXT and Surveil Co-pack are not registered for sale or use in all states. FulTime NXT, Keystone LA NXT, Keystone NXT, SureStart II and Surpass NXT 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. Do not fall-apply anhydrous ammonia south of Highway 16 in the state of Illinois. Enlist E3 soybeans are being jointly developed by MS Technologies and Dow AgroSciences. Regulatory approvals are pending for the Enlist herbicide solution and crops containing Enlist herbicide tolerance traits. The information presented here is not an offer for sale. Always read and follow label directions. ©2014 Dow AgroSciences LLC