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Be Aggressive On
Weed Resistance

One of the best defenses against development of herbicide-resistant weeds in cotton just might be to take the offense against them. Using crop rotations, mixing herbicide modes-of-action and relying on selective tillage can go a long way toward preventing or managing resistant weeds.

This is especially the case for the growing number of southern producers who rely on herbicide tolerant technology. Roundup Ready Flex technology has been rapidly adopted by cotton producers who appreciate its wider application window and the time the system saves them.

Being proactive on weed resistance management is a key guard against the development of troublesome glyphosate-resistant weeds to preserving the full benefits of the technology for years to come.

“Roundup Ready Flex cotton allows producers the flexibility to manage weed populations and can easily be incorporated into a weed resistance strategy on the farm,” says Paul Callaghan, cotton traits marketing manager for Monsanto. “The system can help fight not only glyphosate-resistant weeds, but ALS- and triazine-resistant weeds as well. There are some producers who have adopted very successful strategies on their farms.”

Flexibility To Add Residuals

Georgia cotton producer Bobby Smith had approximately 3,000 acres of Roundup Ready Flex cotton in 2007 on his farming operation near Sylvania in Screven County. He currently has to manage around glyphosate-resistant Palmer amaranth, a problem that a number of Georgia cotton producers wrestle with.

“We probably have fewer problems with resistant pigweed than many of our neighbors, and in that respect we are very lucky,” Smith says. “We use a number of herbicides with different modes of action in our cotton, and we’re also able to get some control of pigweed in our peanuts, which reduces the infestation level when we rotate back to cotton.”

Peanut herbicides used include Valor, StrongArm and Cadre. In cotton, which is planted strip-till, Smith uses a burndown application with a Roundup agricultural herbicide, followed by a preplant residual herbicide such as Prowl, which is applied with preplant fertilizer. Smith follows with another application of Prowl in a band at planting and two over-the-top applications with Roundup WeatherMax.

“We also never skimp on our rates of Roundup herbicide,” says the Georgia producer. “We always use the full, labeled rate to ensure the best possible weed control.”

Different Modes Of Action

Dr. Alan York, Extension weed specialist for North Carolina State University, says that residual herbicides are strongly recommended in Roundup Ready Flex cotton.

“It is important to use different herbicide modes of action and to rely more on residual herbicides, whether they are applied preplant, preemergence over the top or at layby,” he says.

York also recommends that a herbicide such as 2,4-D should be incorporated into preplant burndown herbicide treatments when possible. Dicamba provides good control of marestail but must be used carefully due to the predominance of tobacco greenhouses in North Carolina.

“Growers should use some type of preemergence herbicide and include a residual herbicide in at least one over-the-top application of Roundup,” York says. “Residual herbicides can also be added to tankmixes with Roundup for post-directed layby applications.”

Osborn & Barr, which represents Monsanto, provided information for this article.

Important Advantages Of RR Flex System

• Providing an excellent tool to manage ALS and other weed resistance to different herbicide chemistries.

• Increased application flexibility. This means that producers can apply Roundup herbicide formulations over the top of weeds at the right time in Roundup Ready Flex cotton.

• Allows producers to match timing to weed size without having to worry about impacting yield potential.

• Ability to now use higher rates of Roundup PowerMax and Roundup WeatherMax – up to 32 ounces per acre – if needed to provide control.

• Compatible tankmix partner with other chemistries used for residual control.

• Provides the best opportunity to start clean and stay clean throughout the season.

“As a company solely focused on agriculture, Monsanto is committed to preserving the Roundup Ready system for the long run – because we know that our success is only based on the producers’ success,” says Callaghan. “That’s why we are committed to bringing the producers the most comprehensive information that they need for effective weed resistance management.”

Source: Paul Callaghan, Cotton Traits Marketing Manager, Monsanto

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