Pre-emergent herbicides proved useful for farmers in 2019.
Caleb Dalley, NDSU Hettinger Research Extension Center (HREC) weed scientist, is in his fifth year at the center conducting weed control and herbicide trials.
Many regions in Montana and North Dakota experienced cool weather with heavy precipitation during the growing season.
“With our cool wet conditions (in 2019), weed control results have been much different than in past years when it was hot and dry,” Dalley said.
Dalley spoke to producers about controlling weeds, along with new options for weed control in canola with Bayer’s TruFlex Canola, and weed control trials with safflower and Spartan.
In HREC’s research trials in 2019, Dalley said there was value in using pre-emergent herbicides.
“Pre-emergent herbicides give you a lot of value in a year like last year because farm fields received enough rain for herbicides to be active in the soil,” he said.
Secondly, with frequent rainfall, there were many flushes of weeds emerging.
“If you don’t use a pre-emergent herbicides, you have to deal with these weeds that come up afterward. It becomes more challenging to control weeds post-emergence because there were so many new flushes of weeds,” Dalley said.
In addition, when farmers use pre-emergence herbicides before seeding, there isn’t a need to be in as big of a hurry to apply their in-crop post-emergence herbicides.
The pre-emergence herbicides will reduce the number of weeds, and in some cases, they may eliminate the need for a post-emergence herbicide application.
“When using a burndown that includes a herbicide like Sharpen, that has some residual activity, you are not so pressed to get your post-applications out,” he added.
In 2019, farmers ran into challenges with being able to spray herbicides, including many windy days with rain and coming across so many wet spots in the field.
“It's hard to get a good application across the whole field in these type of conditions,” Dalley said.
Fall applications for weed control
At the HREC, Dalley is conducting research on fall applications for weed control that include pre-emergent herbicides with the fall burndown.
One of those trials looks at controlling downy brome, especially where the weed is a problem.
“The best time to control downy brome is in the fall. Putting down a fall application sometime in mid-October is an ideal time for controlling downy brome,” he said.
With fall burndown applications, utilizing pre-emergence herbicides in the mix also helps reduce the number of weeds coming up in the spring.
Producers are also able to transition into planting where they don’t have to worry so much about putting down an application right away to control downy brome and other annual weeds, according to Dalley.
TruFlex canola coming out
A new variety of canola, TruFlex canola from Bayer, is going to be available in 2020.
“TruFlex canola has a higher level of tolerance to glyphosate, so you can use the full rate of glyphosate,” Dalley said. “It is going to be a benefit to canola growers because current Roundup Ready varieties can only use a pint of glyphosate per acre, which is not as effective.”
According to Bayer, the TruFlex trait will allow for higher glyphosate rates and a wider application window. That will help when farmers are faced with windy weather or a late flush of weeds, which can delay spraying.
“We’re seeing more tolerance to glyphosate with some of the tough weeds, including kochia,” he said. “So having the option of using a higher level of glyphosate with TruFlex canola is going to be a benefit.”
Bayer says TruFlex canola will allow for greater control of a wider spectrum of weed species, including annuals, perennials and harder-to-kill weeds like Canada thistle.
TruFlex canola will also be available stacked with the Liberty Link trait, giving it tolerance to these two post-emergence herbicides.
“I think having two options for post-emergence weed control is going to help a lot,” Dalley said.
Weed control in safflower
Recently, safflower was labeled for the herbicide Spartan Charge, a combination of carfentrazone-ethyl and sulfentrazone.
“It’s a good pre-emergence herbicide for many broadleaf weeds, and there are not a lot of other herbicide options for broadleaf weed control in safflower,” he said.
But with Spartan Charge, producers must make sure they have the right soil type before they are able to apply it.
“If you have a high pH soil, it is not a herbicide for you. If you have lower organic matter (OM), less than 3 percent, it may not be a herbicide for you,” Dalley said. “You need to have a lower soil pH – ideally at or below 7, but at a maximum of 7.5. The higher your soil pH, the greater risk of injury to the safflower”
The herbicide also cannot be used on a coarse soil, such as sandy soils.
“You can’t use it on a sandy soil, but it’s a good option for safflower growers with the right soils types if you need to control broadleaf weeds,” he said.
Research at HREC is looking at tolerance to Spartan with three different varieties of safflower.
“There seems to be a difference in tolerance of safflower varieties to Spartan Charge,” Dalley said.
They are looking at three different varieties, one with moderate tolerance, one with low-tolerance and one with high-tolerance to Spartan Charge, and examining tolerance at rates ranging from 2-8 ounces per acre.
Spartan Charge is currently labeled for 2.5-5 ounces per acre, depending on soil type.
“We are seeing very good tolerance to Spartan Charge in one of the varieties called Cardinal,” he said.
The other varieties have lower or only moderate tolerance to Spartan Charge.