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Managing Weeds and Other Sunflower Pests in 2002

Tuesday, April 2, 2002
filed under: Weeds

Managing Weeds and Other Sunflower Pests in 2002

Spartan Receives Another Section 18, Beyond to be labeled in 2003

Spartan (sulfentrazone) has received Section 18 emergency registration by the Environmental Protection Agency, allowing the product to be used again this year as a weed control management tool in sunflower.

This is the third year for the Section 18 label for Spartan, manufactured by FMC Corporation. EPA is expected to grant a full Section 3 label for sunflower in time for the 2003 growing season. The herbicide has gained considerable popularity among sunflower producers, especially those practicing a minimum till system.

The Section 18 exemption allows a single ground application of Spartan at a rate of 2.67 to 5.33 ounces of product per acre, applied before planting.

The product controls most annual small-seeded broadleaf weeds, such as kochia, pigweed species, lambsquarters, nightshade, smartweed, Russian thistle and biennial wormwood and may suppress buckwheat, mustard, ragweed, and Russian thistle. Spartan may provide some grass control.

Use higher rates if applied up to 30 days prior to planting. Sunflower has good tolerance to Spartan on medium to fine textured soils with organic matter above 3%. Crop injury may occur on soils with low organic matter and soil pH greater than 8.0 Do not use the product on coarse textured soils with less than 1% organic matter.

Research has shown excellent weed control in many different environments throughout the Great Plains region. However, consistent control of sensitive broadleaf weeds and control of grass and marginally susceptible broadleaf weeds greatly depends on at least 0.75 inches of rainfall shortly after application and before weeds emerge, according to North Dakota State University.

Thus, consider applying Spartan well ahead of planting, up to two weeks beforehand, says Ron Meyer, Colorado State University extension agronomist, Burlington, Colo. He adds that CSU plot trials have demonstrated good weed control with no herbicide injury using Spartan at both 2 and 3 oz. rates. In soils with a pH of 7.5 or higher, he recommends using the 2 oz. rate.

Spartan is a PPO inhibitor mode of action herbicide, in which no weed resistance has been documented.

Growers should keep in mind that poor growing conditions at and following sunflower emergence, cold temperatures, soil compaction, or application rate that’s too high based on soil type and organic matter may result in sunflower injury. Make sure furrows are closed at planting to help minimize injury.

Applicators must follow all directions, precautions and warnings on the product label and have a copy of the exemption label in their possession during application.

Clearfield® Label Delayed Until 2003

Canadian regulatory officials recently informed BASF that additional data will be needed for Clearfield® sunflower to meet their Plant Novel Traits (PNT) regulations. Canada is the only country currently regulating introduction of non-GMO crop traits such as Clearfield. BASF has already obtained PNT approval for four other Clearfield crops, and has developed much of the data package necessary to ensure a timely PNT approval for Clearfield sunflower in time for the 2003 season, according to company officials.

Because of these additional regulatory requirements, an emergency exemption (Section 18) for Beyond herbicide use in Clearfield sunflower will not be available in North Dakota or South Dakota in 2002. It is anticipated that regulatory requirements will be met for the 2003 use season, and that Clearfield sunflower will be available in limited supplies next year. Sunflower-producing states may then choose to request emergency exemptions for Beyond use on Clearfield sunflower for hard to manage weeds like marsh elder and cocklebur.

We had hoped to have this hurdle behind us in time for the 2002 season,” says Mark Dahmer, BASF Clearfield Development Project Manager). “BASF will use this season to demonstrate the effectiveness of the herbicide program and hybrid performance in small plot research across the sunflower growing region.”

Non-biotech sunflower having tolerance to the sulfonylurea herbicide Express is being developed by Pioneer and DuPont. It is expected to be commercially released within a few years.

What’s registered in 2002

A list of labeled seed treatment, herbicide, and insecticide options available to sunflower producers in 2002 can be found on the National Sunflower Association web site, Or call the NSA office, 1-888-718-7033.

The NDSU 2002 Weed Control Guide, along with other NDSU Extension weed/herbicide publications and a status of treatments receiving Section 18 approval for 2002, can be found on the NDSU Weed Science web site, More NDSU Crop Production info can be found online at:

Crop pest treatment information can also be found at University and extension service web sites for other leading sunflower producing states:

Colorado State University

Kansas State University

South Dakota State University

University of Minnesota

University of Nebraska

Texas A&M

Don’t Lose to the Easy Weeds

Field surveys in the Dakotas last year indicated volunteer small grains and grassy weeds evident in a number of sunflower fields. Survey organizers found this puzzling, since there is a good selection of pre-emergent (Prowl, Sonalan, Trifluralin) and post-applied (Poast, Select) herbicide products to choose from for grass control in sunflower.

Review weed problems in 2001 in the article “What Were Your Weeds, and Where Were They?” from the December, 2001 issue of The Sunflower. The article can be found on the NSA web site, Click on the link to The Sunflower magazine, then “the archives.” Look under the “weeds” category.

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