Greensboro, North Carolina
March 31, 2004

Satellite-derived surface wetness anomalies - North America.
Standardized (gamma) anomalies for April 30 to May 6, 2003.
Base period 1988-2002.

This satellite map image shows a key week during last year's wetter-than-normal planting season.

New herbicide warranty plans and weed resistance management practices offer growers fresh ideas and practical steps to battle against a variety of production uncertainties this year.

[For a link to the satellite image, go to: http://lwf.ncdc.noaa.gov/servlets/SSMIBrowser. 
Type in these values on the form on p1: Type: Anomaly. Region: North America. Product: Wetness, Time Resolution: Weekly; Year: 2003. Click 'View Images,' then select week 4/30/2003.]

Aside from seed washouts, last year's wet weather brought muddy fields and weed escapes, including amaranth species, such as pigweed and waterhemp, and resistant horseweed (marestail) in places. While weed escapes are often caused by other factors, any seeds from glyphosate-tolerant or -resistant weeds already in the seedbank will likely emerge this spring when conditions are favorable, researchers say.

Weed specialists in Ohio, Indiana, and Kentucky all report increasing pressure from glyphosate-resistant marestail (see sidebar).

"There's a good chance that glyphosate-resistant marestail is increasing from what we've heard from dealers and growers last season," says James Martin, extension weed specialist of the University of Kentucky.

Scientists recognize that excessive use of any herbicidal mode of action increases selection pressure for resistant weeds, and glyphosate-resistant weeds can appear even if there was no apparent problem the year before.

"Resistant marestail seed can blow in from another farm, and that does happen. But I can tell you a lot of our growers routinely apply glyphosate for burndown and then use it one or two more times 'over the top' of the [Roundup Ready(R) [RR(TM)] soybean] crop," says Weed Extension Specialist Jeff Stachler of Ohio State University.

The U.S. Department of Agriculture reports that more than 80 percent of U.S. soybean acreage is planted to RR and other glyphosate-tolerant varieties. Glyphosate-herbicides, such as Touchdown Total(TM) and
Roundup(R) brands, are widely used in more than 230 crops and essential for 'over the top' weed control in RR crop systems. They control a broad spectrum of weeds, offer environmental advantages, and are gentle on RR crops.

Managing Production Risks

To help RR growers manage against glyphosate-resistant weeds, Syngenta Crop Protection advises growers to use 'Best Weed Management Practices.' Syngenta developed the practices with input from university weed-management experts, and now prints them on the label of all its new glyphosate herbicides, including Touchdown Total and Touchdown HiTech(TM). The practices are available from many farm dealers and at: www.syngentacropprotection.com/prod/herbicide/TouchdownTotal. Click on 'Stewardship' and 'Resistance Management'.
 

"Following the 'Best Weed Management Practices' can significantly delay glyphosate-resistant weeds so it's important for dealers and consultants to be informed and make the best recommendation," says Chuck Foresman technical business manager for Syngenta. A consistent approach to controlling specific weed pressure also can potentially preserve up to 16 percent of farmland value. That's according to estimates from farm managers and rural appraisers in a national survey. The independent study, commissioned by Syngenta, was conducted last year. Of course, resistant weeds are just one of many risks RR growers face. Since seed-trait costs are part of the investment for RR crops, many growers and dealer-applicators insist on a glyphosate herbicide with a warranty. Syngenta, for example, backs its new Touchdown Total with a comprehensive warranty through the Touchdown Assurance Plan (TAP) that includes replant burndown coverage (for almost any reason, including weather), as well as crop safety and trait protection coverage. The 2004 program also includes new benefits for RR soybean growers, as well as product options for growers who do not need RR trait coverages or want to shoulder that risk themselves. "It's nice to know that assurance is there if you need it," says Charles Craig who farms RR soybeans in Owensboro, Kentucky. For us, [TAP] helps plan our costs. We pay once for Touchdown at the beginning of the season, and with the cost-control coverage we pretty much know what our weed control costs are going to be." The new assurance program allows growers to make the best agronomic choices for their farm. By following 'Best Practices,' growers avoid excessive selection pressure for glyphosate-resistant weeds. Applications of glyphosate over a two-year period are capped at two for RR soybeans. After that, any warranty applications are exclusively with herbicides that use alternative modes of action. Survivors from the Wild The only way to know for certain if a specific weed population is resistant is through a greenhouse study. Seeds grown from survivors in the field are treated at higher-than normal rates of the herbicide. The Weed Science Society of America defines herbicide resistance "as the inherited ability of a plant to survive and reproduce following exposure to a dose of herbicide normally lethal to the wild type." So, simply put, any next-generation weeds that survive more than the normal rate used to kill the wild type in the field are, in fact, resistant. "Most RR growers don't want to mess with sampling and testing. They just want dead weeds," says sales manager Jeff Houchins of Royster-Clark, Inc. in Decker, Indiana. "We usually spray with either Touchdown or Roundup and sometimes a residual herbicide to take out any survivors." Phil Logsdon, R&D manager of Miles Farm Supply, in Owensboro, Kentucky, notes that growers can be reluctant to change. "But it's our responsibility as an industry to make recommendations for alternative methods to keep this from happening in our farmers' fields," he says. In addition to rotating herbicides with alternative modes of action, he recommends, scouting, tilling to remove problem weeds, and fall herbicides such as Princep(R) herbicide.

THE TALE OF THREE STATES Multiple-Resistant Horseweed (Marestail) in Ohio Soybean In February, Ohio State University researcher Jeff Stachler confirmed the first 'multiple-resistant' horseweed (marestail) in the U.S. The biotype is resistant to both glyphosate and ALS herbicides. Ohio counties with glyphosate-resistant marestail climbed from four to 17 last year and the resistant weed is present on at least 250,000 acres. Indiana Mapping Glyphosate Resistance In Indiana, Purdue is undertaking a statistical survey of counties to determine the extent of glyphosate-resistant marestail in the state. It was first identified in one county in 2002, and was confirmed in at least four counties last year. Survey results are due in April. Resistant Marestail in Kentucky University of Kentucky Weed Scientist Bill Witt, Ph.D., is completing a follow-up greenhouse study from marestail in western Kentucky that survived 1.5 to two times the normal rate of glyphosate in the field last year. He's testing at higher rates, with results due in early April. Marestail resistant to two to four times the normal rate of glyphosate was confirmed in central Kentucky in 2001.

Like the cool wet weather of '03, there will always be risks in farming. The one-two punch of a crop assurance plan plus managing against resistant weeds before they erupt is a strategy that can minimize production risks and costs, and help preserve the productive value of the farm.

Touchdown(R), Touchdown Total(TM), Touchdown HiTECH(TM), LUMAX(R),
Princep(R) are trademarks of a Syngenta Group Company. Roundup(R) and Roundup Ready(R) are registered trademarks of Monsanto Technology LLC. RR(TM) is a trademark of Monsanto Technology LLC.

Visit www.weedresistance.com for more information about managing against glyphosate resistant weeds.