Agricultural Tips In Weed-Control Technologies; Biotechnology To Manage Herbicide-Resistant Weeds

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The development and spread of weeds that are resistant to herbicides is not a new phenomenon, and to date farmers and the agricultural industry have been able to manage herbicide-resistant weeds. This has been accomplished by cotton growers who have used a combination of the latest agricultural biotechnology, improved production methods and timely use of herbicides to effectively manage herbicide-resistant weeds.

Some weeds and grasses have, over time, developed resistance to a number of widely used herbicide chemistries, including atrazine, ALS inhibitors, dinitroanalines and

glyphosate. These resistant weeds and grasses include Palmer amaranth pigweed, marestail or horseweed and at least two species of ryegrass. Some of these weeds species, particularly Palmer amaranth, are resistant to more than one herbicide chemistry, making this herbicide-resistant weed a special concern for cotton growers.

Left uncontrolled, Palmer amaranth pigweed can spread across cotton fields in just a few growing seasons. It is a major problem for cotton growers in several parts of the Cotton Belt, most notably Georgia and North Carolina, and is of growing concern in parts of the Mississippi Delta. Cotton growers have had to get more aggressive in their control efforts, relying more on crop rotations, using different herbicide chemistries and weed-control technologies on infested fields.

Advances in cotton biotechnology, combined with other stewardship methods employed in cotton production, have allowed farmers to reduce the total amount of pesticides – both herbicides and insecticides – that are needed to produce the high cotton yields and quality fiber that are needed in today´s global marketplace. At the same time, these biotechnologies contribute to steadily increasing cotton yields due to improved weed and insect control.

One of the primary tools that cotton growers are using to fight herbicide-resistant weeds such as Palmer amaranth is rotation of herbicide chemistries and using more residual herbicides. The weed science academic community at most Southern land-grant universities believes that herbicide resistance can be selected for when farmers place too much reliance on a single herbicide or herbicide chemistry. Using multiple modes of action and different classes of chemistry – especially in cotton – is one of the best ways to combat herbicide-resistant weeds and manage their spread.

To help cotton growers in their battle against herbicide-resistant weeds, St. Louis-based Monsanto has a program that both incentivizes and rewards cotton growers for using residual herbicides at multiple points during the growing season in Roundup Ready® and Genuity™ Roundup Ready Flex cotton systems. Called the Roundup Ready Cotton Performance Plus Program, this effort helps underwrite some of the cost of using specified residual herbicides before or at planting, over the top during early and midseason, and again in post-directed applications at layby. Monsanto includes herbicides from several different suppliers and, in fact, does not produce or sell any of the qualifying residual herbicides. A grower participating in the program can receive up to $12.50 per acre from Monsanto to help defray the cost of using these other products for weed management.

University researchers in Arkansas, Georgia, North Carolina, Louisiana, Tennessee, Texas and Mississippi highlight the following measures that cotton growers can take for proactive management of herbicide-resistant weeds:

• Always start the season clean with one or more of the following: tillage, a burndown herbicide or a preplant or preemergence herbicide.

• Use residual herbicides at more than one point during the growing season, with application timing options being preplant, preemergence, at planting, over the top and post directed.

• Always rotate herbicide chemistries and herbicides with different modes of action.

• Use full, labeled herbicide rates. Reducing rates can result in variable control and increase the development of herbicide-resistant weeds.

• Tillage can be an option for problem fields.

Following these academic recommendations in weed-control programs and using the Monsanto Genuity™ family of biotech traits, cotton growers can continue to manage herbicide-resistant weeds and optimizing their yield and profitability. To learn more about Genuity™ current and future technology products, visit www.genuity.com.

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