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Marestail in Soybeans: Strategies for the Best Control

By Sarah Lancaster

Controlling marestail in soybeans continues to be a big challenge for Kansas no-till producers. Application timing and weed size are critical factors for successful control of this weed that germinates in the fall or early spring. Research has shown that up to 80% of marestail can die over the winter as a result of cold temperatures and/or lack of adequate moisture. In addition, a well-established cover crop in the fall can further reduce marestail establishment and survival and often is quite effective for marestail control. However, marestail that does survive is often robust and can be difficult to control with herbicides, especially later in the spring. Herbicide options are also limited by widespread resistance to glyphosate and/or ALS-inhibiting (group 2) herbicides in marestail.

Glyphosate-resistant marestail

Figure 1. Glyphosate-resistant marestail in soybeans.

Early spring options

Recent observations suggest marestail in Kansas will bolt (Figure 2, right) in April throughout most of the state, so timing control before the end of March is recommended. In the early spring, using a Group 4 (growth regulator) herbicide such as 2,4-D and/or dicamba is an inexpensive and effective option to control rosette marestail (Figure 2, left). Dicamba has provided better marestail control than 2,4-D and will also provide some residual control, especially at higher use rates. Haluxifen (Elevore) is a newer group 4 herbicide that can provide similar marestail control to dicamba. In addition to targeting smaller weeds, application of group 4 herbicides also generally allows adequate time ahead of planting soybeans to meet required pre-plant intervals.

Using herbicides with longer residual helps control weeds that germinate between treatment and soybean planting. Products that include chlorimuron (Classic, Canopy), cloransulam (FirstRate), flumioxazin (Valor, others), saflufenacil (Sharpen, Optill, Verdict), or metribuzin, can help provide residual control against several broadleaf species, including marestail. However, it is very important to consult and follow the herbicide label guidelines for the required pre-plant intervals prior to planting soybeans as well as the proper rate for your soil.

 

Marestail

Figure 2. Marestail in the rosette growth stage (left photo) versus bolted (right photo).

Pre-plant options

As soybean planting nears, existing marestail plants can become difficult to control because plants will have bolted and be considerably larger. Herbicides to apply as a burndown prior to planting include tank mixes of glyphosate with 2,4-D, and the residual products listed above.

Be very careful to follow label directions regarding plant-back restriction when applying group 4 herbicides ahead of soybean, which can range from 7-30 days depending on the herbicide rate and formulation, as well as soybean variety, precipitation, and geography.

One additional herbicide to consider as a rescue burndown application to control bolting marestail prior to soybean planting is glufosinate (Liberty and others). Although, it would be better to control marestail at an earlier stage of growth, glufosinate has been one of the most effective herbicides to control bolting marestail. Glufosinate also has broad spectrum non-selective activity on other broadleaf and grass species if treated at a young growth stage. Glufosinate is primarily a contact herbicide, so a spray volume of 15 gallons per acre or greater generally provides the most consistent weed control. Glufosinate tends to work best under higher humidity and warm, sunny conditions at application.

Post-emergence options

Controlling marestail in the growing soybean crop can be the biggest challenge for producers, especially in soybeans without herbicide-resistant traits or in glyphosate-resistant soybeans (if marestail is glyphosate resistant). The most successful treatments for large marestail in Roundup Ready soybeans have been tank-mixes of glyphosate with herbicides containing chlorimuron or cloransulam. However, marestail may also be ALS-resistant, and thus not controlled by those herbicides either.

If Roundup Ready 2 Xtend or XtendFlex soybeans are planted, Xtendimax, FeXapan, and Engenia should be some of the most effective herbicides for post-emergence control of marestail in soybeans. Remember that Xtendimax, FeXapan, and Engenia can only be applied to Xtend soybeans. Similarly, Enlist One or Enlist Duo will be effective control options in Enlist E3 soybeans. One final post-emergence option to consider is glufosinate. Glufosinate resistance is in Liberty Link, Enlist E3, and XtendFlex varieties.

Source : ksu.edu

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Moving Ag Research Forward Through Collaboration

Video: Moving Ag Research Forward Through Collaboration



BY: Ashley Robinson

It may seem that public and private researchers have different goals when it comes to agricultural research. However, their different strategies can work in tandem to drive agricultural research forward. Public research may focus more on high-risk and applied research with federal or outside funding, while private sector researchers focus more on research application.

“For me, the sweet spot for public private sector research is when we identify problems and collaborate and can use that diverse perspective to address the different aspects of the challenge. Public sector researchers can work on basic science high risk solutions as tools and technologies are developed. They then can work with their private sector partners who prototype solutions,” Mitch Tuinstra, professor of plant breeding and genetics in Purdue University’s Department of Agronomy, said during the Jan. 10 episode of Seed Speaks.

Public researchers they have the flexibility to be more curiosity driven in their work and do discovery research. This is complimentary to private research, which focuses on delivering a product, explained Jed Christianson, canola product design lead for Bayer CropScience, explained during the episode.

“As a seed developer, we worry about things like new crop diseases emerging. Having strong public sector research where people can look into how a disease lifecycle cycle works, how widespread is it and what damage it causes really helps inform our product development strategies,” he added.

It’s not always easy though to develop these partnerships. For Christianson, it’s simple to call up a colleague at Bayer and start working on a research project. Working with someone outside of his company requires approvals from more people and potential contracts.

“Partnerships take time, and you always need to be careful when you're establishing those contracts. For discoveries made within the agreement, there need to be clear mechanisms for sharing credits and guidelines for anything brought into the research to be used in ways that both parties are comfortable with,” Christianson said.

Kamil Witek, group leader of 2Blades, a non-profit that works with public and private ag researchers, pointed out there can be limitations and challenges to these partnerships. While private researchers are driven by being able to make profits and stay ahead of competitors, public researchers may be focused on information sharing and making it accessible to all.

“The way we deal with this, we work in this unique dual market model. Where on one hand we work with business collaborators, with companies to deliver value to perform projects for them. And at the same time, we return the rights to our discoveries to the IP to use for the public good in developing countries,” Witek said during the episode.

At the end of the day, the focus for all researchers is to drive agricultural research forward through combining the knowledge, skills and specializations of the whole innovation chain, Witek added.

“If there's a win in it for me, and there's a win in it for my private sector colleagues in my case, because I'm on the public side, it’s very likely to succeed, because there's something in it for all of us and everyone's motivated to move forward,” Tuinstra said.