ISSUE 16    August 18, 2005

HERBICIDE RESISTANT WEEDS

Hereís a quick note on herbicide resistance. If you didnít see the press release, a weed scientist at the University of Georgia, Stanley Culpepper, and Monsanto are investigating "probable" glyphosate resistant Palmer amaranth that were found in a few Roundup Ready cotton fields in central Georgia in 2004. At this point, they are conducting heritability tests to determine if the resistance trait is carried from one generation to the next before officially declaring the biotype glyphosate-resistant. The reason this may be of interest is because Palmer amaranth is in the same genus as our pigweeds and waterhemp. This amaranthus genus has evolved resistance to many herbicides, just like triazine-resistant smooth pigweed or the ALS resistant waterhemp. Palmer amaranth is more vigorous and competitive than our pigweed species. Fortunately, Palmer amaranth is more frequent in the southern states such as the region from Kansas to the Carolinas. I do not know of any Palmer amaranth in the entire Plains or Great Plains region.

Of course, glyphosate resistance is not the only resistance concern. Calls were received on herbicide failures caused by the occurrence of several ACC-ase and ALS-resistant weeds this summer as well. All of these situations should serve as reminders that rotation of herbicide mode of action will be beneficial to protect the long-term use of all of our herbicides.

 

DONíT USE SEED FROM GLYPHOSATE TREATED FIELDS

Canadian researchers caution growers not to use pulse crop seed from plants treated with glyphosate from harvest aid or preharvest applications. Glyphosate residues in seed can severely impact germinating seed and seedlings. Results include reduced seedling vigor due to development of an abnormal root system. Roots can be gnarled, twisted, donít branch out or develop lateral roots or root hairs. Few or no nodules form and nitrogen is not fixed no matter how much inoculant was applied.

 

GLYPHOSATE RAINFASTNESS

Scientists from the University of Wisconsin conducted glyphosate rainfast tests on June 30 to see if rain after applications of Roundup WeatherMax or Glystar Plus affected lambsquarters control. In the experiment, they applied full rates (0.75 lb ae/a glyphosate) at 30 minutes, 1, 2, and 4 hours before we simulated a rain. The simulated rain was 1,000 gallons of water applied with a field sprayer equipped with floodjet nozzles. In the experiment, the lambsquarters height had a large range, but averaged about 10 inches tall. Despite the large size, lambsquarters control was good at 3 weeks after application where water was not applied. However, control was reduced with all of the simulated rainfall timings. With the 30 minute timing, control was much less than 50%. Control improves with the 2 and 4 hour delays before rainfall, but some lambsquarters plants are still escaping control.

The reduced control with the simulated rainfall may not be as great under less stressful conditions (ie. smaller lambsquarters or with better soil moisture). However, the experiment clearly demonstrates that lambsquarters needs 4 hours or more before a rain to reach full control under some field conditions. The timing of rainfall after glyphosate applications should be considered as a possible cause for escaping lambsquarters.

 

2,4-D UPDATE

A press release just came out from the Industry Task Force on 2,4-D that summarized the EPAís reregistration decision on 2,4-D. The bottom line is that EPA will continue to support the registration of 2,4-D and that 2,4-D does not present risks of concern to human health when label instructions are followed. There will be a few label changes such as lowering the maximum rates that homeowners can use, but all existing uses are going to be maintained plus three new crops will even be added to the label.

Many people are familiar with the concerns of potential links of 2,4-D to cancer. This is the EPA statement that described the current evaluation of that potential linkage: "The Agency has twice recently reviewed epidemiological studies linking cancer to 2,4-D. In the first review, completed January 14, 2004, EPA concluded there is no additional evidence that would implicate 2,4-D as a cause of cancer (EPA, 2004). The second review of available epidemiological studies occurred in response to comments received during the Phase 3 Public Comment Period for the 2,4-D RED.

EPAís report, dated December 8, 2004 and authored by EPA Scientist Jerry Blondell, Ph.D., found that none of the more recent epidemiological studies definitively linked human cancer cases to 2,4-D." If you are really in to classifications, EPA specifically ranks 2,4-D as a category D chemical, i.e., not classifiable as to human carcinogenicity.

 

ROUNDUP READY ALFALFA APPROVED FOR USE

USDA-APHIS granted approval for sale and use of Roundup Ready alfalfa on June 14, 2005 and the following day the EPA approved the labels to use Roundup for weed control in Roundup Ready alfalfa forage and hay production. State approvals of labels for to use Roundup Original MAX and Roundup WeatherMAX herbicides on Roundup Ready alfalfa are expected by August 1, 2005.

Forage Genetics International and Monsanto have secured import approvals for Mexico, and are anticipating import approvals for Canada and Japan in the fall of 2005. These approvals are expected prior to the first harvest of Roundup Ready alfalfa forage in the spring of 2006. Regulatory submissions have also been made to other import markets, including Korea and Taiwan.

However, because necessary import approvals by independent regulatory agencies cannot be guaranteed, FGI and Monsanto are working together to initially commercialize Roundup Ready alfalfa through licensees under a "Limited Domestic Launch." Under the LDL, FGI and Monsanto will broadly license Roundup Ready alfalfa to seed companies for initial sales in the fall 2005 planting season. Multiple Roundup Ready varieties will be sold to fit fall-dormant and non-dormant market needs.

To implement and communicate the Limited Domestic Launch requirements, all potential seed buyers (forage growers) must have a valid Monsanto Technology/ Stewardship Agreement (MTA), and in addition, they must agree and ensure that the forage produced from the Roundup Ready alfalfa forage field will be used on-farm, or sold to an entity that will certify on-farm use within the United States. This Seed and Feed Use Agreement (SFUA, a domestic containment agreement) will be signed by both the seed dealer and the seed buyer. The SFUA is an enforceable plan that is referenced in the in the product's Monsanto Technology Use Guide (TUG).

It is unclear how much Roundup Ready alfalfa seed might be available in North Dakota. Eventually most seed companies that currently sell alfalfa will have RR varieties in their portfolio. For the immediate future, the seed supply will plant between 50,000 and 75,000 acres nationwide. My guess is that much of the summer and fall seeding of RR alfalfa will be on the west coast but certainly some seed will be available in important alfalfa growing states.

What is the value of this gene in alfalfa to our producers?

Weed management will be easier. But with summer seedings we seldom need or use herbicides. So to plant a RR alfalfa variety now would essentially put the gene "in storage" until weeds appear in the later the rotation. This is fine as long as use of glyphosate at a later time results in returns (or other benefits) that are greater than those of alternative herbicides (or of not treating with any herbicide). With spring seedings of RR alfalfa, the gene would be used as needed in the first year to ensure a weed-free start to the life of the alfalfa stand and would then be available for use in the third or later years of the stand if and when needed.

What is the cost?

This has been the big question from the beginning. No one expected the technology fee to be low and that expectation is realized. East of the Rocky Mountains, the one-time technology fee per 50-lb bag of Roundup Ready alfalfa seed is $125. West of the Rockies, it is $150 a bag. If a grower plants 12 lb/acre, the tech fee is approximately $30/A. Add to this the cost of the seed itself to get the total seed cost. Be sure and ask for information on all the important traits you need in top performing alfalfa varieties in the Dakotas (disease and insect resistance/ tolerance, winter hardiness, etc.) in assessing the value of these varieties to you.

This is certainly a significant event as itís the first genetically engineered perennial crop to receive regulatory approval. Without a doubt, other biotech traits in alfalfa will follow. The rate of initial adoption will probably be slow to assess the relative benefits, performance and longevity of the RR alfalfa varieties available as we enter this new era. Few expect the long term adoption level in the midwest to reach those of RR soybeans but without a doubt this technology will find a place on some and perhaps many situations.

Richard Zollinger
NDSU Extension Weed Specialist
r.zollinger@ndsu.edu


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