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Using Reduced Rates of Spartan

Saturday, April 15, 2006
filed under: Weeds

A second year of research by weed scientists Alan Helm of Colorado State University and Brien Henry of USDA-ARS near Akron, Col., again demonstrated excellent weed control (including kochia) with Spartan down to 1 oz (see list of treatment combinations and results).

Helm and Henry conducted their research in 2005 at the USDA-ARS Central Great Plains Research Station at Akron. The six treatment comparisons are described in Table 1. Pre-plant applications of Spartan (Sulfentrazone) and Prowl H2O were made on August 5, (11 days before planting). Dwarf Clearfield sunflower (Triumph TRX 3345CL) was planted on August 16. Glyphosate was applied as a burndown 14 days prior to the preplant applications. Beyond was applied on September 1 at the V-4 growth stage.

Weed control evaluations were made on September 1, 12, and 26 (Helm notes that the study was conducted in the fall since the intention was to evaluate weed control, not to take the trials to harvest). Figures 1, 2, and 3 show weed control by date. On September 1, all pre-plant applications of Prowl H2O and Spartan provided at least 96% control of redroot pigweed and 93% control of puncturevine. Beyond applied on September 1, increased control of redroot pigweed and puncturevine to 80% in the Beyond alone treatment. Treatments 5 and 6 included two rates of Spartan (2 and 1 oz/ac respectively). These treatments were not statistically different season long. This indicates that reduced rates of Spartan are as effective as the standard rate, says Helm.

Phil Stahlman, weed specialist at Kansas State University, also has data which shows good results with Spartan at reduced rates ¡V weed control effectiveness down to 1 oz/ac was just as good as the 3 oz/ac rate. If using a reduced rate of Spartan, Stahlman advises tank-mixing it with Prowl (or Pendimax) or Prowl H20 at the full labeled rate. ¡§Spartan¡¦s strength is on the broadleaves, Prowl¡¦s strengths is on the grasses,¡¨ he says.

Using reduced rates of Spartan is not recommended in the Northern Plains. ¡§Soil pH, organic matter, and soil type are all part of the equation, and they have that in their favor in the High Plains,¡¨ says NDSU¡¦s Zollinger. ¡§Kochia is one of the more sensitive weeds to Spartan, that¡¦s in the grower¡¦s favor,¡¨ he continues. ¡§If you have high pH, light sandy soil with less than 1% organic matter, you may have good luck with lower rates of Spartan up here with good moisture for activation. Even if you have the soil pH to support it, we do have some pretty high organic matter out there, even as far west as Bismarck. And even in a medium-textured soil, the herbicide can get absorbed and tied up in the organic matter and clay particles. Then you can have marginal weed control.¡¨

Manufacturer FMC has discontinued making the dry flowable Sulfentrazone herbicide, Spartan„µ 75DF, in favor of the liquid formulation, Spartan 4F. While Sulfentrazone was in short supply in 2005, supply of Spartan 4F is expected to be adequate to meet industry demand in 2006. ¡V Tracy Sayler

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