December 7, 2015
Controlling weeds in soybean fields this past summer was a challenge for most farmers across the Midwest, often due to untimely rain, and lots of it. Agronomists from WinField share what they saw in fields and talk about the challenges, and some successes, that soybean farmers had with weeds this year.
Ohio
2015 challenges
For soybeans, harder-to-control weeds and resistance were the biggest challenges in 2015. Joe Rickard, WinField agronomist, reports that resistance continues to worsen in this crop. Farmers who have accepted this are using a preemergence herbicide.
Across the state of Ohio, marestail is a continuing problem and Rickard also saw more Palmer amaranth this past crop season in soybean fields.
Success stories
Even though each operation is different, Rickard noticed farmers who applied preemerge herbicides had cleaner fields than those who did not. While there are a list of good soybean pre-residual products, one key product that Rickard recommends leaving in the tank mix is 2,4-D. “Yes, there is a waiting period to get back in and plant, but the benefits are worth it,” he explains.
Rickard also reminds farmers to spray weeds when they are small, which is crucial for weed control.
Michigan
2015 challenges
Marestail is a growing weed problem for soybean farmers in Michigan, reports Corey Guza. Frequent and at times, heavy rainfall reduced the effectiveness of preemergence herbicides and challenged growers when making timely postemergence weed control applications. Weed size was an issue with farmers as they tried to manage weeds later than normal. In addition to marestail being an issue throughout the state, Southern Michigan had issues with common waterhemp and giant ragweed, while common ragweed and common lambsquarters were issues in central and northern Michigan.
Success stories
Farmers in Michigan have been adopting strategies to rotate multiple modes of action when using herbicides for weed control. This has slowed the rate at which herbicide resistant weeds are spreading, relative to other states. They are also incorporating pre and postemerence weed control strategies within the same season, which also will improve the chance of success with their herbicide programs, Guza says.
Indiana
2015 challenges
The biggest challenge in 2015 was simply getting herbicide applications on the field, reports agronomist Jason Roth, WinField. In Roth’s territory of northern Indiana, fall conditions in 2014 favored neither tillage nor fall burndowns, and spring conditions in 2015 weren’t any better.
He saw some soybean farmers skip a burndown and residual application, hoping to clean up their fields after planting. However, the onslaught of rain prevented timely, or sometimes any, applications. Areas that experienced heavy rainfall accumulated drown-out spots, which became strongholds for weeds.
Similar to cornfields, many soybean fields were infested with marestail, waterhemp, Palmar amaranth, lambsquarters and giant ragweed. “Some of these weeds are prolific seed producers and the seed bank received many reinforcements for a battle with farmers over the next few years, unfortunately,” says Roth.
Success stories
Regarding summer annual weeds, farmers with the best weed control and cleanest fields continue to implement multiple passes and overlapping residuals. This includes applying soil residual products around planting, and then making an early post application to extend the soil residual window. “Overlapping residuals is becoming absolutely essential in battling waterhemp and Palmer amaranth, because these weeds continue to germinate and emerge later in summer,” Roth says. The best programs also used multiple modes of action to help combat the development of herbicide resistance, he adds.
Wisconsin
2015 challenges
Waterhemp continues to be a serious problem for soybean production, says Todd Cardwell, WinField agronomist. Waterhemp together with common lambsquarters made up the bulk of weed challenges for Wisconsin soybean farmers this season.
If farmers who used glyphosate alone on lambsquarters and couldn’t spray before weeds were more than 3 or 4 inches tall, control was difficult. Timing was critical, he adds, since hot, dry weather fostered fast growth of lambsquarters.
Success stories
Farmers who were successful implemented a weed-control program that used preplant or preemergent herbicides, followed by cleanup spray with glyphosate and additional burner-type chemistries mixed into the tank. This approach, Cardwell says, usually provided a fairly clean field with two passes.
South Dakota
2015 challenges
Herbicide-resistant waterhemp has bedeviled South Dakota soybean farmers after taking hold in the eastern part of the state over the last couple of seasons, says Ryan Wolf, WinField agronomist. As you head west in the state, the annual broadleaf kochia has also become resistant, Wolf says.
Success stories