Late Winter Kochia Control in Fields Going to Soybeans, Sunflowers, and Wheat

Mar 04, 2021

By Sarah Lancaster and Vipan Kumar

This is the third and final article in a series discussing pre-emergence herbicides for kochia control. This week we will discuss recommendations specific to fields that will be planted to soybean or sunflower this spring and wheat in the fall. Previous articles have discussed general considerations for late-winter kochia control (https://bit.ly/2MWvSrD - Issue 837) and pre-emergence herbicides for kochia control in fields that will be planted to corn or grain sorghum (https://bit.ly/3tKKZp3 - Issue 838).

Fields going to soybeans

Start in February or early March with a tank-mix of glyphosate (using a minimum of 0.75 lb ae/acre) or Gramoxone SL (minimum of 2 pts/acre) and 8 to 16 oz/acre of Clarity prior to kochia emergence. The use of Clarity requires a minimum accumulation of 1 inch of rain and then 28 days prior to planting soybeans, except in case of Roundup Ready 2 Xtend or XtendFlex soybeans. As indicated by the label, Clarity cannot be used as a pre-plant treatment in soybeans in areas with less than 25 inches of annual rainfall. Paraquat tank-mixed with metribuzin (Dimetric, others) will provide extended residual control of kochia, as long as the population of kochia is susceptible to triazine herbicides. Be aware of rate restrictions for metribuzin in western KS, as soil and environmental characteristics influence the potential for soybean injury following metribuzin.

Sulfentrazone-based products (Spartan, others) could also be considered for use prior to kochia emergence to manage an early flush of kochia (Figures 1 and 2). However, it’s important to note the crop rotation restrictions on these products. Pyroxasulfone (Zidua) also has activity on kochia, although more rain is required for activation. Figure 1 illustrates the efficacy of various pre-emergence herbicide programs for controlling glyphosate- and dicamba-resistant kochia in Roundup Ready 2 Xtend soybeans planted in no-till dryland fields at Hays, KS. These treatments were applied to emerged kochia on May 23. All treatments also included Roundup PowerMax.

Kochia control

Figure 1. Kochia control following pre-emergence herbicide application in no-till dryland soybean in Hays, KS (WAA= weeks after application).

Kochia control in non-treated plot

Figure 2. Kochia control in non-treated plot (A) and with PRE applied Spartan (B) in Roundup Ready 2 Xtend soybean at 7 weeks after treatment (WAT).

Fields going to sunflowers

Planting sunflowers into a clean seedbed is a key step to achieving good season-long control of all broadleaf and grassy weeds. But, it is especially important for getting good control of any weed populations, such as kochia, that are resistant to glyphosate or ALS-inhibiting herbicides and cannot be controlled with post-emergence herbicides-applied herbicides in sunflower.

The best approach to control ALS/glyphosate-resistant kochia in sunflower is to start in February/early March with a tank-mix of Gramoxone (using a minimum of 2 pts/acre) and Spartan, Spartan Charge (sulfentrazone+Aim), Broadaxe or Authority Elite (sulfentrazone+Dual Magnum), or Authority Supreme/Authority Edge (sulfentrazone+Zidua) before kochia begins to germinate. Select pre-emergence products that are effective on kochia and apply additional pre-emergence herbicides at planting to extend control of kochia and other weeds. Dicamba is not an option in these applications, due to label restrictions. Monitor fields closely as additional Gramoxone SL treatments may be required prior to sunflower planting.

Fields going to fall-planted wheat

If kochia is emerging in fields to be planted to wheat this fall, atrazine cannot be used. Metribuzin can substitute for atrazine and has a 4-month plant-back restriction to wheat. Additional products include Scoparia or Authority MTZ and products containing sulfentrazone or isoxaflutole. Zidua also has good activity but requires significant rainfall for activation, so it should be applied with dicamba.

Source : ksu.edu

Video: Can Gene Editing Give Seeds a Stronger Start?

Reagan Reed has a way of describing his research that might make a plant breeder pause.

“I’m the sort of person who likes to break things to understand them,” he says.

What he breaks are genes involved in seed germination. Reed, a Ph.D. candidate at the University of California, Davis, is investigating whether changing those genes can help seeds establish healthy plants under a wider range of conditions.

Reed recently attended the National Association for Plant Breeding meeting in College Station, Texas, as an NAPB Borlaug Scholar. His work speaks to a question that matters well beyond a research lab: what does it take for a seed to get a crop off to a strong start?

A seed that germinates quickly, alongside the others planted with it, spends less time vulnerable to stresses before seedlings become established.

“If you’re able to bridge that gap between germination to stand establishment, then that’s going to give you the highest probability of having a solid yield that year,” Reed says. “There’s a bunch that can go wrong after that, but it maximises your yield from the start, at least.”

Reed works in Dr. Imtiyaz Khanday’s lab at UC Davis, where his research focuses on seed quality in tomatoes and potatoes. He brings an unusual academic background to the work: at Skidmore College, he studied both biology and Latin.

Reed believes that combination prepared him for research. Translating an ancient text means studying each word, weighing its possible meanings and using context to reach the best interpretation. There is rarely a way to know with complete certainty what an author intended. Science, he says, requires a similar willingness to work through uncertainty.

“Attention to detail and comfortability working with uncertainty,” is how he sums up what Latin taught him.

In the lab, uncertainty can produce a surprise. Reed describes changing one gene and seeing little effect. Changing a second gene also appears to do little. Put both changes in the same genetic background, though, and the result can be substantial.

“I break this gene, nothing really happens. I break this other gene, nothing really happens. I combine them into the same genetic background, and now there’s a massive effect,” he says.

Those interactions matter as researchers gain the ability to edit multiple genes at once. They also complicate any simple account of how a trait works: improving a seed may depend on understanding what several genes do together.

For Reed, the question is whether that knowledge could help seeds germinate reliably when conditions are difficult. Some of the genes he studies prevent germination under certain conditions. That response may serve a plant well in one setting while limiting its usefulness in agriculture. He wants to learn what happens when those genes are changed, and whether the result improves establishment.

Yet a discovery that works in a lab still has a long way to travel before it reaches a field. Reed argues that agricultural biotechnology faces an economic challenge as well as a scientific one. New tools can create value for farmers, he says, but developing them requires a way to support the work in an industry where margins can be thin.

His fellowship with Flagship Pioneering gave him a view across AI, agriculture-related work and human health research. It also reinforced the importance of bringing people with different expertise into the same conversation—a benefit of gatherings such as the NAPB meeting.

“You need to have a team of people with different backgrounds who are willing to work together and approach the same problem in different perspectives and different ways,” he says.

That thinking connects the different parts of Reed’s path. Latin taught him to examine details without expecting a perfect answer. Gene editing lets him test what individual genes do—and what happens when their effects combine. Working with people beyond his own field helps him ask what those findings could become.

He came to agriculture because of its reach: the possibility that work by a small group of researchers could eventually make a difference on a much larger scale. His immediate focus is smaller and more precise. He wants to understand what helps a seed get through its first days and become a healthy plant.