Cotton herbicides in jeopardy

Cotton farmers battling glyphosate resistant weeds may take another shot, if the Environmental Protection Agency (EPA) follows through on plans to ban arsenic-containing herbicides.

DSMA and MSMA, both popular pre-Roundup Ready herbicides are among the products on the chopping block.

In the Aug. 9, 2006 Federal Register (Volume 71, Number 153), the agency stated: This notice announces the availability of EPA's Reregistration Eligibility Decision (RED) for the organic arsenical herbicides MSMA, DSMA, CAMA, and cacodylic acid, and opens a public comment period on this document. The Agency has determined that all products containing MSMA, DSMA, CAMA, and cacodylic acid are not eligible for reregistration.

This posting in the Federal Register follows the original posting June 5, 2006), seeking public assistance in determining risks. In this posting the EPA sought public assessment of the risk from arsenic-based herbicides. The June 5, notice stated: EPA is developing a Reregistration Eligibility Decision (RED) for the organic arsenic herbicides through a modified, 4-Phase public participation process that the Agency uses to involve the public in developing pesticide reregistration and tolerance reassessment decisions.

Based on initial input, or lack of it from the farmer's perspective, the agency appears to have made the decision to end registration of traditional cotton herbicides that contain arsenic compounds.

MSMA and DSMA, prior to Roundup Ready technology, were used for a wide spectrum of weed and grass control. These materials are especially effective against cocklebur, lambsquarters and other small-seeded weeds, plus nutsedge and annual grasses in cotton.

Though not officially documented, researchers are fairly sure they have isolated glyphosate resistant lambsquarters. If this resistance is documented and proves to be widespread, arsenic-based herbicides would be the least cost, most effective management tools available to farmers.

“We used a lot of MSMA and DSMA before we had Roundup Ready cotton,” notes Virginia cotton grower Dean Stallings. Stallings and fellow Smithfield, Va., farmer Robbie Taylor say these materials have not been widely used in their area in recent years because of the effectiveness of glyphosate-based herbicides in controlling these pests.

“If we lose MSMA and DSMA, and if lambsquarters is resistant to glyphosate, it would be an economic loss for us,” Taylor says.

In the USDA's document, MSMA, DSMA, CAMA, and cacodylic acid are collectively referred to as organic arsenical herbicides. Though use on cotton has dropped dramatically since the onset of Roundup Ready technology, DSMA and MSMA are primary herbicides for use in turf management and highway rights of way.

While EPA has identified some risk associated with the direct use of these herbicides, the Agency's primary concern is the potential for applied organic arsenical products to transform to a more toxic inorganic form of arsenic in soil with subsequent transport to drinking water.

There is little doubt that farmers, turf managers and others concerned about the loss of arsenic-based herbicides can send their comments to the EPA by Oct. 10, 2006. Comments must be identified by docket identification (ID) number EPA-HQ-OPP-2006-0201, by one of the following methods:

  • E-mail to and follow on-line instructions.

  • Mail to: Office of Pesticide Programs, Regulatory Public Document (7502P), Environmental Protection Agency, 1200 Pennsylvania Avenue, NW, Washington D.C. 20460-0001.

  • Deliver to the EPA, Room S-4400, One Potomac Yard (South Building) 2777 South Crystal Drive, Arlington, Va.

For more information about the upcoming EPA decision on arsenic-based herbicides, those interested can call the Docket Facility telephone number — 703-305-5805.

Information sent to EPA will be included in their entirety, according to information in the Federal Register. All the comments can be accessed online, and anonymously, at Personal information or proprietary business information should not be included in submissions, since these will be published as part of the commentary.

For cotton farmers from North Carolina to Florida, who are already dogged by resistance of Palmer amaranth pigweed to glyphosate, the loss of arensic-based herbicides will be another restriction in their efforts to survive in a glyphosate resistant world.

First documented in 2005, resistance of Palmer pigweed to glyphosate appears to be more widespread in 2006 than was expected. Marestail, common ragweed, Italian ryegrass and other weed and grass species are now suspect for glyphosate resistance in different areas of the Southeast.

Clemson University Weed Scientist Chris Main says MSMA and DSMA are products that we don't really know a great deal about, though they have been around a long time. Main explains that these herbicides are used almost exclusively, on cotton, with other herbicides.

On cocklebur, MSMA is very good, he says, adding that there are arsenic-resistant cocklebur.

Layby application will give good burndown of nutsedge and other grasses. MSMA has a place in cotton weed control, but to champion keeping a material that is potentially a threat to humans is tough to do, Main explains.

From the EPA's perspective arsenic getting into the water supply is a realistic threat to the environment.

For weed scientists in the Southeast, the issue is a difficult tightrope to walk. Of primary concern is the environment and public health, but they also are pledged to help farmers manage weed problems in the most economic way possible.

If the arsenicals are removed from the marketplace, it will likely be a similar process through which Bladex was removed — happening in a phase-out over two or three years. For farmers who feel these herbicides are critical to their farming survival, the opportunity is there to have a say in the final decision.

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