Full Spartan Label to Allow Fall Application
EPA expected to approve both Section 18 and full Section 3 label for Spartan on sunflower in 2003
Sunflower producers have become accustomed to using Spartan (sulfentrazone) for controlling annual small-seeded broadleaf weeds, such as kochia, pigweed, lambsquarters and nightshade.
Technically, however, it’s not labeled yet.
2002 marked the fourth year that Spartan received a Section 18 emergency registration label by the Environmental Protection Agency. The conditional use must be applied for by agricultural officials from sunflower-producing states, allowing the product to be used as a weed control management tool in sunflower for control of kochia.
The EPA is expected to approve a full Section 3 label sometime in 2003, but likely not in time for planting in 2003. Thus, Sam Tutt, northern technical manager for FMC Corp, which makes Spartan, anticipates that sunflower states will again need to apply for a Section 18 label for Spartan to be used next spring.
In other words, it’s likely Spartan will receive a fifth (and final) Section 18 emergency registration label in time for use at planting next spring, then full Section 3 label approval sometime in 2003.
Tutt expects directions under the full label will be similar to those under Section 18 usage. A key difference: the full label will permit Spartan to be applied in the fall, a beneficial option for many no-till sunflower producers, as that will permit a wider window of application.
“We know that fall application of Spartan works very well because we have a federal label for post-harvest or fall application that is being used extensively in Montana for chemical fallow situations, or where producers plan to rotate to small grains,” says Tutt.
Until EPA grants full label use of Spartan for sunflower, a 12-month use interval remains in effect. With full label approval, a four-month rotation interval to small grains will be allowed.
Spartan performs best applied pre-emerge on the soil surface, and incorporation is not recommended. Like any pre-emerge herbicide, moisture is needed for activation, and this was a common problem in many drought-affected sunflower growing areas in 2002. Applying Spartan as early in the spring as possible gives a better chance for getting moisture for activation, says Tutt. Under the pending Section 18 exemption renewal, early spring application can be made up to 30 days prior to planting.
Tutt says Spartan can be tank mixed with glyphosate (Roundup) or Prowl (pendimethalin). “It’s important to remember that when mixing Spartan, use the full labeled rate of glyphosate for maximum uptake. Some might be tempted to cut rates because they’re using two weed control products, but these two products have different modes of activity. Spartan is not a foliar contact herbicide like glyphosate. It works below ground, not above ground. Glyphosate kills weeds that have already emerged. Spartan controls weeds as they emerge; in fact the weeds that are being controlled by Spartan can be so small it can be difficult to see them.”
As many sunflower growers already know, recommended application rates for Spartan may vary depending on soil type and organic matter. Sunflower has good tolerance to Spartan on different soils, from coarse to fine textured soils with organic matter from 1.5 to 3.5 % as long as producers follow use rate (Section 18 exemption) guidelines. The product shouldn’t be used on coarse textured soils with less than 1% organic matter.
“Coarse soils with low organic matter call for lower use rates. Higher pH’s, greater than 7.5, also enable a greater degree of activation than lower pH soils, but
moisture remains one of the key ingredients for successful activation,” says Tutt. “A common question from producers is what rate to use in a field with variable soil types. The simple answer is to use the lower end of the application rate range listed in the exemption guidelines to ensure there are no crop response problems.”
Research has shown excellent weed control with Spartan in many different environments throughout the sunflower production region. However, consistent control of sensitive broadleaf weeds depends on 0.5 to 0.75 inches of rainfall shortly after application and before weeds emerge, according to North Dakota State University. – Tracy Sayler
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