Start Clean Or Start Over

Soybean farmers across the Mid-South plan strategies to control glyphosate-resistant weeds. The ultimate goal is to keep the crop healthy and the yield strong.

It’s almost spring planting season, and that means it’s time for soybean growers in the Mid-South to fine-tune their plan of attack for glyphosate-resistant weeds. Despite unpredictable weather patterns and market conditions, one constant remains at the forefront in keeping the crop healthy – using an effective preemergence herbicide as the first line of defense against yield-robbing weeds.

“Start clean or start over,” said Frank Carey, Field Market Development Specialist for Valent USA.

Valor and Fierce Herbicide brands, for instance, allow for consistent, broad-spectrum control against Palmer amaranth, Italian ryegrass, horseweed, henbit and others.

Combat Inconsistent Weather


This Mississippi field appears to be pigweed-free eight weeks after a Fierce herbicide application.
This Mississippi field appears to be pigweed-free eight weeks after a Fierce herbicide application.

Weather always plays a key role in weed control. The more rainfall during the latter part of the season, the harder it is to get herbicides out in a timely fashion. If temperatures warm up prematurely and make for an early spring, weeds will germinate quicker.

Dr. Trey Koger manages the agronomic operations for Silent Shade Planting Company, an 8,500-acre corn, soybean, rice, cotton, and peanut row-crop farm in Belzoni, Miss. The main problem weeds in his fields are horseweed, morning glories, barnyardgrass, and the top resistance culprit, Palmer amaranth.

“We have a lot of modes of action that are going across all of our fields on an annual basis,” Koger said. “That helps us to manage glyphosate-resistant weeds.”

Rather than being at the mercy of the weather, Koger makes every attempt to apply a preemergence herbicide seven to 21 days prior to planting to increase the likelihood of an activating rainfall.

“Having an herbicide activated the day you plant is critical for all of our crops, including soybeans,” Koger said, “so that you are not planting a crop and the crop’s coming up at the same timeframe as the weed.”

Do the Math for Timely Control

With a preemergence herbicide like Valor or Fierce factored into weed management programs, soybean growers are able to use the numbers to their advantage when it comes to pigweeds, which in ideal conditions can grow an inch a day.

“If you let pigweed get ahead of you, you have already lost the battle,” Carey said. “Once you get behind, you’re behind for the whole season.”

Say a grower has one million pigweeds per acre – with the 99 percent control of a PRE, he/she is down to 10,000 weeds spread out over that acre. Then, the grower can look forward to four to six weeks of residual to have adequate time for the second round of postemerge herbicides like Cobra, Phoenix and SelectMax.

“If you don’t use a PRE and you get one million pigweeds coming up, there’s absolutely no way you can get the control you need with a postemergence application in a timely fashion,” Carey said.

Don’t skimp on PREs

While soybean growers have seen a positive yield track over the last several seasons, the price of beans is down compared to years past. Even with low commodities and high inputs, the cost of PREs are not that significant compared to many other inputs in budgets, Koger said.

“Everything has gone up,” he said. “But if you look at the costs of the herbicide inputs versus what we get in return, especially in areas like the Mississippi Delta where we’re dealing with resistant weeds, I don’t see how you can take that out of your budget.”

Instead, Koger recommends other methods of reducing expenses, like cutting back on seeding rates, or trying to be more judicious with irrigation, fertility inputs, labor and/or machinery.

In addition to budgetary diligence, soybean growers should use an Integrated Pest Management approach and be proactive in their specific management decisions. “

A lot of times, a grower doesn’t go looking for help until he’s got a problem,” Carey said. “By the time he’s got a problem, it’s too late.”

To Koger, several factors add up to mitigating glyphosate-resistant weeds in conjunction with PRE applications: using tillage to work the ground up; hand-hoeing prior to seed development; and maintaining excellent fertility levels as well as timely irrigation practices.

“It helps us to get the crop out of the ground and get it to canopy closure as quickly as possible,” Koger said. “Canopy closure is our biggest weed defense ally.”

This article was submitted by Valent U.S.A. Corp. PR.

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